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regcomp.c: Some code paths didn't terminate an inversion list iteration
[perl5.git] / regcomp.c
index 9ad1409..2eba109 100644 (file)
--- a/regcomp.c
+++ b/regcomp.c
 #define PERL_IN_REGCOMP_C
 #include "perl.h"
 
-#ifndef PERL_IN_XSUB_RE
-#  include "INTERN.h"
-#endif
-
 #define REG_COMP_C
 #ifdef PERL_IN_XSUB_RE
 #  include "re_comp.h"
@@ -135,6 +131,8 @@ struct RExC_state_t {
     char       *parse;                 /* Input-scan pointer. */
     char        *copy_start;            /* start of copy of input within
                                            constructed parse string */
+    char        *save_copy_start;       /* Provides one level of saving
+                                           and restoring 'copy_start' */
     char        *copy_start_in_input;   /* Position in input string
                                            corresponding to copy_start */
     SSize_t    whilem_seen;            /* number of WHILEM in this expr */
@@ -167,6 +165,7 @@ struct RExC_state_t {
     I32                seen_zerolen;
     regnode_offset *open_parens;       /* offsets to open parens */
     regnode_offset *close_parens;      /* offsets to close parens */
+    I32      parens_buf_size;           /* #slots malloced open/close_parens */
     regnode     *end_op;                /* END node in program */
     I32                utf8;           /* whether the pattern is utf8 or not */
     I32                orig_utf8;      /* whether the pattern was originally in utf8 */
@@ -183,6 +182,7 @@ struct RExC_state_t {
                                            through */
     U32         study_chunk_recursed_bytes;  /* bytes in bitmap */
     I32                in_lookbehind;
+    I32                in_lookahead;
     I32                contains_locale;
     I32                override_recoding;
 #ifdef EBCDIC
@@ -197,6 +197,7 @@ struct RExC_state_t {
     scan_frame *frame_last;
     U32         frame_count;
     AV         *warn_text;
+    HV         *unlexed_names;
 #ifdef ADD_TO_REGEXEC
     char       *starttry;              /* -Dr: where regtry was called. */
 #define RExC_starttry  (pRExC_state->starttry)
@@ -231,6 +232,7 @@ struct RExC_state_t {
 #define RExC_precomp   (pRExC_state->precomp)
 #define RExC_copy_start_in_input (pRExC_state->copy_start_in_input)
 #define RExC_copy_start_in_constructed  (pRExC_state->copy_start)
+#define RExC_save_copy_start_in_constructed  (pRExC_state->save_copy_start)
 #define RExC_precomp_end (pRExC_state->precomp_end)
 #define RExC_rx_sv     (pRExC_state->rx_sv)
 #define RExC_rx                (pRExC_state->rx)
@@ -256,6 +258,7 @@ struct RExC_state_t {
 #define RExC_maxlen        (pRExC_state->maxlen)
 #define RExC_npar      (pRExC_state->npar)
 #define RExC_total_parens      (pRExC_state->total_par)
+#define RExC_parens_buf_size   (pRExC_state->parens_buf_size)
 #define RExC_nestroot   (pRExC_state->nestroot)
 #define RExC_seen_zerolen      (pRExC_state->seen_zerolen)
 #define RExC_utf8      (pRExC_state->utf8)
@@ -271,6 +274,7 @@ struct RExC_state_t {
 #define RExC_study_chunk_recursed_bytes  \
                                    (pRExC_state->study_chunk_recursed_bytes)
 #define RExC_in_lookbehind     (pRExC_state->in_lookbehind)
+#define RExC_in_lookahead      (pRExC_state->in_lookahead)
 #define RExC_contains_locale   (pRExC_state->contains_locale)
 #ifdef EBCDIC
 #   define RExC_recode_x_to_native (pRExC_state->recode_x_to_native)
@@ -284,6 +288,7 @@ struct RExC_state_t {
 #define RExC_warn_text (pRExC_state->warn_text)
 #define RExC_in_script_run      (pRExC_state->in_script_run)
 #define RExC_use_BRANCHJ        (pRExC_state->use_BRANCHJ)
+#define RExC_unlexed_names (pRExC_state->unlexed_names)
 
 /* Heuristic check on the complexity of the pattern: if TOO_NAUGHTY, we set
  * a flag to disable back-off on the fixed/floating substrings - if it's
@@ -355,7 +360,7 @@ struct RExC_state_t {
             if (DEPENDS_SEMANTICS) {                                        \
                 set_regex_charset(&RExC_flags, REGEX_UNICODE_CHARSET);      \
                 RExC_uni_semantics = 1;                                     \
-                if (RExC_seen_d_op && LIKELY(RExC_total_parens >= 0)) {     \
+                if (RExC_seen_d_op && LIKELY(! IN_PARENS_PASS)) {           \
                     /* No need to restart the parse if we haven't seen      \
                      * anything that differs between /u and /d, and no need \
                      * to restart immediately if we're going to reparse     \
@@ -366,11 +371,10 @@ struct RExC_state_t {
             }                                                               \
     } STMT_END
 
-#define BRANCH_MAX_OFFSET   U16_MAX
 #define REQUIRE_BRANCHJ(flagp, restart_retval)                              \
     STMT_START {                                                            \
                 RExC_use_BRANCHJ = 1;                                       \
-                if (LIKELY(RExC_total_parens >= 0)) {                       \
+                if (LIKELY(! IN_PARENS_PASS)) {                             \
                     /* No need to restart the parse immediately if we're    \
                      * going to reparse anyway to count parens */           \
                     *flagp |= RESTART_PARSE;                                \
@@ -378,10 +382,19 @@ struct RExC_state_t {
                 }                                                           \
     } STMT_END
 
+/* Until we have completed the parse, we leave RExC_total_parens at 0 or
+ * less.  After that, it must always be positive, because the whole re is
+ * considered to be surrounded by virtual parens.  Setting it to negative
+ * indicates there is some construct that needs to know the actual number of
+ * parens to be properly handled.  And that means an extra pass will be
+ * required after we've counted them all */
+#define ALL_PARENS_COUNTED (RExC_total_parens > 0)
 #define REQUIRE_PARENS_PASS                                                 \
-    STMT_START {                                                            \
-                    if (RExC_total_parens == 0) RExC_total_parens = -1;     \
+    STMT_START {  /* No-op if have completed a pass */                      \
+                    if (! ALL_PARENS_COUNTED) RExC_total_parens = -1;       \
     } STMT_END
+#define IN_PARENS_PASS (RExC_total_parens < 0)
+
 
 /* This is used to return failure (zero) early from the calling function if
  * various flags in 'flags' are set.  Two flags always cause a return:
@@ -698,7 +711,7 @@ static const scan_data_t zero_scan_data = {
 
 /* Used to point after bad bytes for an error message, but avoid skipping
  * past a nul byte. */
-#define SKIP_IF_CHAR(s) (!*(s) ? 0 : UTF ? UTF8SKIP(s) : 1)
+#define SKIP_IF_CHAR(s, e) (!*(s) ? 0 : UTF ? UTF8_SAFE_SKIP(s, e) : 1)
 
 /* Set up to clean up after our imminent demise */
 #define PREPARE_TO_DIE                                                      \
@@ -813,8 +826,13 @@ static const scan_data_t zero_scan_data = {
 } STMT_END
 
 /* Setting this to NULL is a signal to not output warnings */
-#define TURN_OFF_WARNINGS_IN_SUBSTITUTE_PARSE RExC_copy_start_in_constructed = NULL
-#define RESTORE_WARNINGS RExC_copy_start_in_constructed = RExC_precomp
+#define TURN_OFF_WARNINGS_IN_SUBSTITUTE_PARSE                               \
+    STMT_START {                                                            \
+      RExC_save_copy_start_in_constructed  = RExC_copy_start_in_constructed;\
+      RExC_copy_start_in_constructed = NULL;                                \
+    } STMT_END
+#define RESTORE_WARNINGS                                                    \
+    RExC_copy_start_in_constructed = RExC_save_copy_start_in_constructed
 
 /* Since a warning can be generated multiple times as the input is reparsed, we
  * output it the first time we come to that point in the parse, but suppress it
@@ -1546,6 +1564,10 @@ S_ssc_is_cp_posixl_init(const RExC_state_t *pRExC_state,
     return TRUE;
 }
 
+#define INVLIST_INDEX 0
+#define ONLY_LOCALE_MATCHES_INDEX 1
+#define DEFERRED_USER_DEFINED_INDEX 2
+
 STATIC SV*
 S_get_ANYOF_cp_list_for_ssc(pTHX_ const RExC_state_t *pRExC_state,
                                const regnode_charclass* const node)
@@ -1556,11 +1578,15 @@ S_get_ANYOF_cp_list_for_ssc(pTHX_ const RExC_state_t *pRExC_state,
      * returned list must, and will, contain every code point that is a
      * possibility. */
 
+    dVAR;
     SV* invlist = NULL;
     SV* only_utf8_locale_invlist = NULL;
     unsigned int i;
     const U32 n = ARG(node);
     bool new_node_has_latin1 = FALSE;
+    const U8 flags = (inRANGE(OP(node), ANYOFH, ANYOFHr))
+                      ? 0
+                      : ANYOF_FLAGS(node);
 
     PERL_ARGS_ASSERT_GET_ANYOF_CP_LIST_FOR_SSC;
 
@@ -1571,28 +1597,24 @@ S_get_ANYOF_cp_list_for_ssc(pTHX_ const RExC_state_t *pRExC_state,
         SV **const ary = AvARRAY(av);
         assert(RExC_rxi->data->what[n] == 's');
 
-        if (ary[1] && ary[1] != &PL_sv_undef) { /* Has compile-time swash */
-            invlist = sv_2mortal(invlist_clone(_get_swash_invlist(ary[1]), NULL));
-        }
-        else if (ary[0] && ary[0] != &PL_sv_undef) {
+        if (av_tindex_skip_len_mg(av) >= DEFERRED_USER_DEFINED_INDEX) {
 
-            /* Here, no compile-time swash, and there are things that won't be
-             * known until runtime -- we have to assume it could be anything */
+            /* Here there are things that won't be known until runtime -- we
+             * have to assume it could be anything */
             invlist = sv_2mortal(_new_invlist(1));
             return _add_range_to_invlist(invlist, 0, UV_MAX);
         }
-        else if (ary[3] && ary[3] != &PL_sv_undef) {
+        else if (ary[INVLIST_INDEX]) {
 
-            /* Here no compile-time swash, and no run-time only data.  Use the
-             * node's inversion list */
-            invlist = sv_2mortal(invlist_clone(ary[3], NULL));
+            /* Use the node's inversion list */
+            invlist = sv_2mortal(invlist_clone(ary[INVLIST_INDEX], NULL));
         }
 
         /* Get the code points valid only under UTF-8 locales */
-        if ((ANYOF_FLAGS(node) & ANYOFL_FOLD)
-            && ary[2] && ary[2] != &PL_sv_undef)
+        if (   (flags & ANYOFL_FOLD)
+            &&  av_tindex_skip_len_mg(av) >= ONLY_LOCALE_MATCHES_INDEX)
         {
-            only_utf8_locale_invlist = ary[2];
+            only_utf8_locale_invlist = ary[ONLY_LOCALE_MATCHES_INDEX];
         }
     }
 
@@ -1610,22 +1632,26 @@ S_get_ANYOF_cp_list_for_ssc(pTHX_ const RExC_state_t *pRExC_state,
      * actually does include them.  (Think about "\xe0" =~ /[^\xc0]/di;).  We
      * have to do this here before we add the unconditionally matched code
      * points */
-    if (ANYOF_FLAGS(node) & ANYOF_INVERT) {
+    if (flags & ANYOF_INVERT) {
         _invlist_intersection_complement_2nd(invlist,
                                              PL_UpperLatin1,
                                              &invlist);
     }
 
     /* Add in the points from the bit map */
-    for (i = 0; i < NUM_ANYOF_CODE_POINTS; i++) {
-        if (ANYOF_BITMAP_TEST(node, i)) {
-            unsigned int start = i++;
+    if (! inRANGE(OP(node), ANYOFH, ANYOFHr)) {
+        for (i = 0; i < NUM_ANYOF_CODE_POINTS; i++) {
+            if (ANYOF_BITMAP_TEST(node, i)) {
+                unsigned int start = i++;
 
-            for (; i < NUM_ANYOF_CODE_POINTS && ANYOF_BITMAP_TEST(node, i); ++i) {
-                /* empty */
+                for (;    i < NUM_ANYOF_CODE_POINTS
+                       && ANYOF_BITMAP_TEST(node, i); ++i)
+                {
+                    /* empty */
+                }
+                invlist = _add_range_to_invlist(invlist, start, i-1);
+                new_node_has_latin1 = TRUE;
             }
-            invlist = _add_range_to_invlist(invlist, start, i-1);
-            new_node_has_latin1 = TRUE;
         }
     }
 
@@ -1633,25 +1659,40 @@ S_get_ANYOF_cp_list_for_ssc(pTHX_ const RExC_state_t *pRExC_state,
      * as well.  But don't add them if inverting, as when that gets done below,
      * it would exclude all these characters, including the ones it shouldn't
      * that were added just above */
-    if (! (ANYOF_FLAGS(node) & ANYOF_INVERT) && OP(node) == ANYOFD
-        && (ANYOF_FLAGS(node) & ANYOF_SHARED_d_MATCHES_ALL_NON_UTF8_NON_ASCII_non_d_WARN_SUPER))
+    if (! (flags & ANYOF_INVERT) && OP(node) == ANYOFD
+        && (flags & ANYOF_SHARED_d_MATCHES_ALL_NON_UTF8_NON_ASCII_non_d_WARN_SUPER))
     {
         _invlist_union(invlist, PL_UpperLatin1, &invlist);
     }
 
     /* Similarly for these */
-    if (ANYOF_FLAGS(node) & ANYOF_MATCHES_ALL_ABOVE_BITMAP) {
+    if (flags & ANYOF_MATCHES_ALL_ABOVE_BITMAP) {
         _invlist_union_complement_2nd(invlist, PL_InBitmap, &invlist);
     }
 
-    if (ANYOF_FLAGS(node) & ANYOF_INVERT) {
+    if (flags & ANYOF_INVERT) {
         _invlist_invert(invlist);
     }
-    else if (new_node_has_latin1 && ANYOF_FLAGS(node) & ANYOFL_FOLD) {
+    else if (flags & ANYOFL_FOLD) {
+        if (new_node_has_latin1) {
 
-        /* Under /li, any 0-255 could fold to any other 0-255, depending on the
-         * locale.  We can skip this if there are no 0-255 at all. */
-        _invlist_union(invlist, PL_Latin1, &invlist);
+            /* Under /li, any 0-255 could fold to any other 0-255, depending on
+             * the locale.  We can skip this if there are no 0-255 at all. */
+            _invlist_union(invlist, PL_Latin1, &invlist);
+
+            invlist = add_cp_to_invlist(invlist, LATIN_SMALL_LETTER_DOTLESS_I);
+            invlist = add_cp_to_invlist(invlist, LATIN_CAPITAL_LETTER_I_WITH_DOT_ABOVE);
+        }
+        else {
+            if (_invlist_contains_cp(invlist, LATIN_SMALL_LETTER_DOTLESS_I)) {
+                invlist = add_cp_to_invlist(invlist, 'I');
+            }
+            if (_invlist_contains_cp(invlist,
+                                        LATIN_CAPITAL_LETTER_I_WITH_DOT_ABOVE))
+            {
+                invlist = add_cp_to_invlist(invlist, 'i');
+            }
+        }
     }
 
     /* Similarly add the UTF-8 locale possible matches.  These have to be
@@ -1660,7 +1701,7 @@ S_get_ANYOF_cp_list_for_ssc(pTHX_ const RExC_state_t *pRExC_state,
     if (only_utf8_locale_invlist) {
         _invlist_union_maybe_complement_2nd(invlist,
                                             only_utf8_locale_invlist,
-                                            ANYOF_FLAGS(node) & ANYOF_INVERT,
+                                            flags & ANYOF_INVERT,
                                             &invlist);
     }
 
@@ -1685,6 +1726,9 @@ S_ssc_and(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
      * another SSC or a regular ANYOF class.  Can create false positives. */
 
     SV* anded_cp_list;
+    U8  and_with_flags = inRANGE(OP(and_with), ANYOFH, ANYOFHr)
+                          ? 0
+                          : ANYOF_FLAGS(and_with);
     U8  anded_flags;
 
     PERL_ARGS_ASSERT_SSC_AND;
@@ -1695,7 +1739,7 @@ S_ssc_and(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
      * the code point inversion list and just the relevant flags */
     if (is_ANYOF_SYNTHETIC(and_with)) {
         anded_cp_list = ((regnode_ssc *)and_with)->invlist;
-        anded_flags = ANYOF_FLAGS(and_with);
+        anded_flags = and_with_flags;
 
         /* XXX This is a kludge around what appears to be deficiencies in the
          * optimizer.  If we make S_ssc_anything() add in the WARN_SUPER flag,
@@ -1719,14 +1763,14 @@ S_ssc_and(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
     else {
         anded_cp_list = get_ANYOF_cp_list_for_ssc(pRExC_state, and_with);
         if (OP(and_with) == ANYOFD) {
-            anded_flags = ANYOF_FLAGS(and_with) & ANYOF_COMMON_FLAGS;
+            anded_flags = and_with_flags & ANYOF_COMMON_FLAGS;
         }
         else {
-            anded_flags = ANYOF_FLAGS(and_with)
+            anded_flags = and_with_flags
             &( ANYOF_COMMON_FLAGS
               |ANYOF_SHARED_d_MATCHES_ALL_NON_UTF8_NON_ASCII_non_d_WARN_SUPER
               |ANYOF_SHARED_d_UPPER_LATIN1_UTF8_STRING_MATCHES_non_d_RUNTIME_USER_PROP);
-            if (ANYOFL_UTF8_LOCALE_REQD(ANYOF_FLAGS(and_with))) {
+            if (ANYOFL_UTF8_LOCALE_REQD(and_with_flags)) {
                 anded_flags &=
                     ANYOFL_SHARED_UTF8_LOCALE_fold_HAS_MATCHES_nonfold_REQD;
             }
@@ -1766,7 +1810,7 @@ S_ssc_and(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
      *                         <=  (C1 & ~C2) | (P1 & ~P2)
      * */
 
-    if ((ANYOF_FLAGS(and_with) & ANYOF_INVERT)
+    if ((and_with_flags & ANYOF_INVERT)
         && ! is_ANYOF_SYNTHETIC(and_with))
     {
         unsigned int i;
@@ -1778,7 +1822,7 @@ S_ssc_and(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
 
         /* If either P1 or P2 is empty, the intersection will be also; can skip
          * the loop */
-        if (! (ANYOF_FLAGS(and_with) & ANYOF_MATCHES_POSIXL)) {
+        if (! (and_with_flags & ANYOF_MATCHES_POSIXL)) {
             ANYOF_POSIXL_ZERO(ssc);
         }
         else if (ANYOF_POSIXL_SSC_TEST_ANY_SET(ssc)) {
@@ -1838,16 +1882,16 @@ S_ssc_and(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
             else {
                 ssc->invlist = anded_cp_list;
                 ANYOF_POSIXL_ZERO(ssc);
-                if (ANYOF_FLAGS(and_with) & ANYOF_MATCHES_POSIXL) {
+                if (and_with_flags & ANYOF_MATCHES_POSIXL) {
                     ANYOF_POSIXL_OR((regnode_charclass_posixl*) and_with, ssc);
                 }
             }
         }
         else if (ANYOF_POSIXL_SSC_TEST_ANY_SET(ssc)
-                 || (ANYOF_FLAGS(and_with) & ANYOF_MATCHES_POSIXL))
+                 || (and_with_flags & ANYOF_MATCHES_POSIXL))
         {
             /* One or the other of P1, P2 is non-empty. */
-            if (ANYOF_FLAGS(and_with) & ANYOF_MATCHES_POSIXL) {
+            if (and_with_flags & ANYOF_MATCHES_POSIXL) {
                 ANYOF_POSIXL_AND((regnode_charclass_posixl*) and_with, ssc);
             }
             ssc_union(ssc, anded_cp_list, FALSE);
@@ -1868,6 +1912,9 @@ S_ssc_or(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
 
     SV* ored_cp_list;
     U8 ored_flags;
+    U8  or_with_flags = inRANGE(OP(or_with), ANYOFH, ANYOFHr)
+                         ? 0
+                         : ANYOF_FLAGS(or_with);
 
     PERL_ARGS_ASSERT_SSC_OR;
 
@@ -1877,17 +1924,17 @@ S_ssc_or(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
      * the code point inversion list and just the relevant flags */
     if (is_ANYOF_SYNTHETIC(or_with)) {
         ored_cp_list = ((regnode_ssc*) or_with)->invlist;
-        ored_flags = ANYOF_FLAGS(or_with);
+        ored_flags = or_with_flags;
     }
     else {
         ored_cp_list = get_ANYOF_cp_list_for_ssc(pRExC_state, or_with);
-        ored_flags = ANYOF_FLAGS(or_with) & ANYOF_COMMON_FLAGS;
+        ored_flags = or_with_flags & ANYOF_COMMON_FLAGS;
         if (OP(or_with) != ANYOFD) {
             ored_flags
-            |= ANYOF_FLAGS(or_with)
+            |= or_with_flags
              & ( ANYOF_SHARED_d_MATCHES_ALL_NON_UTF8_NON_ASCII_non_d_WARN_SUPER
                 |ANYOF_SHARED_d_UPPER_LATIN1_UTF8_STRING_MATCHES_non_d_RUNTIME_USER_PROP);
-            if (ANYOFL_UTF8_LOCALE_REQD(ANYOF_FLAGS(or_with))) {
+            if (ANYOFL_UTF8_LOCALE_REQD(or_with_flags)) {
                 ored_flags |=
                     ANYOFL_SHARED_UTF8_LOCALE_fold_HAS_MATCHES_nonfold_REQD;
             }
@@ -1914,12 +1961,12 @@ S_ssc_or(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
      * (which results in actually simpler code than the non-inverted case)
      * */
 
-    if ((ANYOF_FLAGS(or_with) & ANYOF_INVERT)
+    if ((or_with_flags & ANYOF_INVERT)
         && ! is_ANYOF_SYNTHETIC(or_with))
     {
         /* We ignore P2, leaving P1 going forward */
     }   /* else  Not inverted */
-    else if (ANYOF_FLAGS(or_with) & ANYOF_MATCHES_POSIXL) {
+    else if (or_with_flags & ANYOF_MATCHES_POSIXL) {
         ANYOF_POSIXL_OR((regnode_charclass_posixl*)or_with, ssc);
         if (ANYOF_POSIXL_SSC_TEST_ANY_SET(ssc)) {
             unsigned int i;
@@ -2038,7 +2085,7 @@ S_is_ssc_worth_it(const RExC_state_t * pRExC_state, const regnode_ssc * ssc)
     U32 count = 0;      /* Running total of number of code points matched by
                            'ssc' */
     UV start, end;      /* Start and end points of current range in inversion
-                           list */
+                           XXX outdated.  UTF-8 locales are common, what about invert? list */
     const U32 max_code_points = (LOC)
                                 ?  256
                                 : ((  ! UNI_SEMANTICS
@@ -2090,8 +2137,7 @@ S_ssc_finalize(pTHX_ RExC_state_t *pRExC_state, regnode_ssc *ssc)
 
     populate_ANYOF_from_invlist( (regnode *) ssc, &invlist);
 
-    set_ANYOF_arg(pRExC_state, (regnode *) ssc, invlist,
-                                NULL, NULL, NULL, FALSE);
+    set_ANYOF_arg(pRExC_state, (regnode *) ssc, invlist, NULL, NULL);
 
     /* Make sure is clone-safe */
     ssc->invlist = NULL;
@@ -2482,7 +2528,8 @@ is the recommended Unicode-aware way of saying
        if (UTF) {                                                         \
             SV *zlopp = newSV(UTF8_MAXBYTES);                             \
            unsigned char *flrbbbbb = (unsigned char *) SvPVX(zlopp);      \
-            unsigned const char *const kapow = uvchr_to_utf8(flrbbbbb, val); \
+            unsigned char *const kapow = uvchr_to_utf8(flrbbbbb, val);     \
+            *kapow = '\0';                                                 \
            SvCUR_set(zlopp, kapow - flrbbbbb);                            \
            SvPOK_on(zlopp);                                               \
            SvUTF8_on(zlopp);                                              \
@@ -2675,7 +2722,7 @@ S_make_trie(pTHX_ RExC_state_t *pRExC_state, regnode *startbranch,
         trie_words = newAV();
     });
 
-    re_trie_maxbuff = get_sv(RE_TRIE_MAXBUF_NAME, 1);
+    re_trie_maxbuff = get_sv(RE_TRIE_MAXBUF_NAME, GV_ADD);
     assert(re_trie_maxbuff);
     if (!SvIOK(re_trie_maxbuff)) {
         sv_setiv(re_trie_maxbuff, RE_TRIE_MAXBUF_INIT);
@@ -3906,7 +3953,7 @@ S_construct_ahocorasick_from_trie(pTHX_ RExC_state_t *pRExC_state, regnode *sour
  *      that a character in the pattern corresponds to at most a single
  *      character in the target string.  (And I do mean character, and not byte
  *      here, unlike other parts of the documentation that have never been
- *      updated to account for multibyte Unicode.)  sharp s in EXACTF and
+ *      updated to account for multibyte Unicode.)  Sharp s in EXACTF and
  *      EXACTFL nodes can match the two character string 'ss'; in EXACTFAA
  *      nodes it can match "\x{17F}\x{17F}".  These, along with other ones in
  *      EXACTFL nodes, violate the assumption, and they are the only instances
@@ -4335,6 +4382,23 @@ S_join_exact(pTHX_ RExC_state_t *pRExC_state, regnode *scan,
            }
 #endif
        }
+
+        if (     STR_LEN(scan) == 1
+            &&   isALPHA_A(* STRING(scan))
+            &&  (         OP(scan) == EXACTFAA
+                 || (     OP(scan) == EXACTFU
+                     && ! HAS_NONLATIN1_SIMPLE_FOLD_CLOSURE(* STRING(scan)))))
+        {
+            U8 mask = ~ ('A' ^ 'a'); /* These differ in just one bit */
+
+            /* Replace a length 1 ASCII fold pair node with an ANYOFM node,
+             * with the mask set to the complement of the bit that differs
+             * between upper and lower case, and the lowest code point of the
+             * pair (which the '&' forces) */
+            OP(scan) = ANYOFM;
+            ARG_SET(scan, *STRING(scan) & mask);
+            FLAGS(scan) = mask;
+        }
     }
 
 #ifdef DEBUGGING
@@ -4393,6 +4457,7 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
                        /* recursed: which subroutines have we recursed into */
                        /* and_withp: Valid if flags & SCF_DO_STCLASS_OR */
 {
+    dVAR;
     /* There must be at least this number of characters to match */
     SSize_t min = 0;
     I32 pars = 0, code;
@@ -5275,6 +5340,27 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
                     OP(next) = EXACTFU;
                 }
 
+                if (     STR_LEN(next) == 1
+                    &&   isALPHA_A(* STRING(next))
+                    && (         OP(next) == EXACTFAA
+                        || (     OP(next) == EXACTFU
+                            && ! HAS_NONLATIN1_SIMPLE_FOLD_CLOSURE(* STRING(next)))))
+                {
+                    /* These differ in just one bit */
+                    U8 mask = ~ ('A' ^ 'a');
+
+                    assert(isALPHA_A(* STRING(next)));
+
+                    /* Then replace it by an ANYOFM node, with
+                    * the mask set to the complement of the
+                    * bit that differs between upper and lower
+                    * case, and the lowest code point of the
+                    * pair (which the '&' forces) */
+                    OP(next) = ANYOFM;
+                    ARG_SET(next, *STRING(next) & mask);
+                    FLAGS(next) = mask;
+                }
+
                if (flags & SCF_DO_STCLASS) {
                    mincount = 0;
                    maxcount = REG_INFTY;
@@ -5553,9 +5639,12 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
                        STRLEN l;
                        const char * const s = SvPV_const(data->last_found, l);
                        SSize_t old = b - data->last_start_min;
+                        assert(old >= 0);
 
                        if (UTF)
-                           old = utf8_hop((U8*)s, old) - (U8*)s;
+                           old = utf8_hop_forward((U8*)s, old,
+                                               (U8 *) SvEND(data->last_found))
+                                - (U8*)s;
                        l -= old;
                        /* Get the added string: */
                        last_str = newSVpvn_utf8(s  + old, l, UTF);
@@ -5763,6 +5852,9 @@ Perl_re_printf( aTHX_  "LHS=%" UVuf " RHS=%" UVuf "\n",
                 case ANYOFD:
                 case ANYOFL:
                 case ANYOFPOSIXL:
+                case ANYOFH:
+                case ANYOFHb:
+                case ANYOFHr:
                 case ANYOF:
                    if (flags & SCF_DO_STCLASS_AND)
                        ssc_and(pRExC_state, data->start_class,
@@ -5919,14 +6011,27 @@ Perl_re_printf( aTHX_  "LHS=%" UVuf " RHS=%" UVuf "\n",
                                       last, &data_fake, stopparen,
                                       recursed_depth, NULL, f, depth+1);
                 if (scan->flags) {
-                    if (deltanext) {
-                       FAIL("Variable length lookbehind not implemented");
-                    }
-                    else if (minnext > (I32)U8_MAX) {
+                    if (   deltanext < 0
+                        || deltanext > (I32) U8_MAX
+                        || minnext > (I32)U8_MAX
+                        || minnext + deltanext > (I32)U8_MAX)
+                    {
                        FAIL2("Lookbehind longer than %" UVuf " not implemented",
                               (UV)U8_MAX);
                     }
-                    scan->flags = (U8)minnext;
+
+                    /* The 'next_off' field has been repurposed to count the
+                     * additional starting positions to try beyond the initial
+                     * one.  (This leaves it at 0 for non-variable length
+                     * matches to avoid breakage for those not using this
+                     * extension) */
+                    if (deltanext) {
+                        scan->next_off = deltanext;
+                        ckWARNexperimental(RExC_parse,
+                            WARN_EXPERIMENTAL__VLB,
+                            "Variable length lookbehind is experimental");
+                    }
+                    scan->flags = (U8)minnext + deltanext;
                 }
                 if (data) {
                     if (data_fake.flags & (SF_HAS_PAR|SF_IN_PAR))
@@ -6011,14 +6116,21 @@ Perl_re_printf( aTHX_  "LHS=%" UVuf " RHS=%" UVuf "\n",
                                         stopparen, recursed_depth, NULL,
                                         f, depth+1);
                 if (scan->flags) {
-                    if (deltanext) {
-                       FAIL("Variable length lookbehind not implemented");
-                    }
-                    else if (*minnextp > (I32)U8_MAX) {
+                    assert(0);  /* This code has never been tested since this
+                                   is normally not compiled */
+                    if (   deltanext < 0
+                        || deltanext > (I32) U8_MAX
+                        || *minnextp > (I32)U8_MAX
+                        || *minnextp + deltanext > (I32)U8_MAX)
+                    {
                        FAIL2("Lookbehind longer than %" UVuf " not implemented",
                               (UV)U8_MAX);
                     }
-                    scan->flags = (U8)*minnextp;
+
+                    if (deltanext) {
+                        scan->next_off = deltanext;
+                    }
+                    scan->flags = (U8)*minnextp + deltanext;
                 }
 
                 *minnextp += min;
@@ -7149,7 +7261,7 @@ S_set_regex_pv(pTHX_ RExC_state_t *pRExC_state, REGEXP *Rx)
         const char* name;
 
         name = get_regex_charset_name(RExC_rx->extflags, &len);
-        if strEQ(name, DEPENDS_PAT_MODS) {  /* /d under UTF-8 => /u */
+        if (strEQ(name, DEPENDS_PAT_MODS)) {  /* /d under UTF-8 => /u */
             assert(RExC_utf8);
             name = UNICODE_PAT_MODS;
             len = sizeof(UNICODE_PAT_MODS) - 1;
@@ -7244,6 +7356,7 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
                    OP *expr, const regexp_engine* eng, REGEXP *old_re,
                     bool *is_bare_re, const U32 orig_rx_flags, const U32 pm_flags)
 {
+    dVAR;
     REGEXP *Rx;         /* Capital 'R' means points to a REGEXP */
     STRLEN plen;
     char *exp;
@@ -7301,6 +7414,7 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
     }
 
     pRExC_state->warn_text = NULL;
+    pRExC_state->unlexed_names = NULL;
     pRExC_state->code_blocks = NULL;
 
     if (is_bare_re)
@@ -7510,6 +7624,7 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
     RExC_seen = 0;
     RExC_maxlen = 0;
     RExC_in_lookbehind = 0;
+    RExC_in_lookahead = 0;
     RExC_seen_zerolen = *exp == '^' ? -1 : 0;
 #ifdef EBCDIC
     RExC_recode_x_to_native = 0;
@@ -7599,6 +7714,7 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
 
     RExC_naughty = 0;
     RExC_npar = 1;
+    RExC_parens_buf_size = 0;
     RExC_emit_start = RExC_rxi->program;
     pRExC_state->code_index = 0;
 
@@ -7608,9 +7724,9 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
     /* Do the parse */
     if (reg(pRExC_state, 0, &flags, 1)) {
 
-        /* Success!, But if RExC_total_parens < 0, we need to redo the parse
-         * knowing how many parens there actually are */
-        if (RExC_total_parens < 0) {
+        /* Success!, But we may need to redo the parse knowing how many parens
+         * there actually are */
+        if (IN_PARENS_PASS) {
             flags |= RESTART_PARSE;
         }
 
@@ -7652,7 +7768,7 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
             DEBUG_PARSE_r(Perl_re_printf( aTHX_ "Need to redo parse\n"));
         }
 
-        if (RExC_total_parens > 0) {
+        if (ALL_PARENS_COUNTED) {
             /* Make enough room for all the known parens, and zero it */
             Renew(RExC_open_parens, RExC_total_parens, regnode_offset);
             Zero(RExC_open_parens, RExC_total_parens, regnode_offset);
@@ -8750,7 +8866,7 @@ S_reg_scan_name(pTHX_ RExC_state_t *pRExC_state, U32 flags)
             /* It might be a forward reference; we can't fail until we
                 * know, by completing the parse to get all the groups, and
                 * then reparsing */
-            if (RExC_total_parens > 0)  {
+            if (ALL_PARENS_COUNTED)  {
                 vFAIL("Reference to nonexistent named group");
             }
             else {
@@ -8765,7 +8881,6 @@ S_reg_scan_name(pTHX_ RExC_state_t *pRExC_state, U32 flags)
 }
 
 #define DEBUG_PARSE_MSG(funcname)     DEBUG_PARSE_r({           \
-    int num;                                                    \
     if (RExC_lastparse!=RExC_parse) {                           \
         Perl_re_printf( aTHX_  "%s",                            \
             Perl_pv_pretty(aTHX_ RExC_mysv1, RExC_parse,        \
@@ -8781,16 +8896,15 @@ S_reg_scan_name(pTHX_ RExC_state_t *pRExC_state, U32 flags)
     } else                                                      \
         Perl_re_printf( aTHX_ "%16s","");                       \
                                                                 \
-    num=REG_NODE_NUM(REGNODE_p(RExC_emit));                     \
-    if (RExC_lastnum!=num)                                      \
-       Perl_re_printf( aTHX_ "|%4d", num);                      \
+    if (RExC_lastnum!=RExC_emit)                                \
+       Perl_re_printf( aTHX_ "|%4d", RExC_emit);                \
     else                                                        \
        Perl_re_printf( aTHX_ "|%4s","");                        \
     Perl_re_printf( aTHX_ "|%*s%-4s",                           \
         (int)((depth*2)), "",                                   \
         (funcname)                                              \
     );                                                          \
-    RExC_lastnum=num;                                           \
+    RExC_lastnum=RExC_emit;                                     \
     RExC_lastparse=RExC_parse;                                  \
 })
 
@@ -9074,9 +9188,7 @@ Perl__new_invlist(pTHX_ IV initial_size)
        initial_size = 10;
     }
 
-    /* Allocate the initial space */
     new_list = newSV_type(SVt_INVLIST);
-
     initialize_invlist_guts(new_list, initial_size);
 
     return new_list;
@@ -9332,100 +9444,6 @@ Perl__invlist_search(SV* const invlist, const UV cp)
 }
 
 void
-Perl__invlist_populate_swatch(SV* const invlist,
-                              const UV start, const UV end, U8* swatch)
-{
-    /* populates a swatch of a swash the same way swatch_get() does in utf8.c,
-     * but is used when the swash has an inversion list.  This makes this much
-     * faster, as it uses a binary search instead of a linear one.  This is
-     * intimately tied to that function, and perhaps should be in utf8.c,
-     * except it is intimately tied to inversion lists as well.  It assumes
-     * that <swatch> is all 0's on input */
-
-    UV current = start;
-    const IV len = _invlist_len(invlist);
-    IV i;
-    const UV * array;
-
-    PERL_ARGS_ASSERT__INVLIST_POPULATE_SWATCH;
-
-    if (len == 0) { /* Empty inversion list */
-        return;
-    }
-
-    array = invlist_array(invlist);
-
-    /* Find which element it is */
-    i = _invlist_search(invlist, start);
-
-    /* We populate from <start> to <end> */
-    while (current < end) {
-        UV upper;
-
-       /* The inversion list gives the results for every possible code point
-        * after the first one in the list.  Only those ranges whose index is
-        * even are ones that the inversion list matches.  For the odd ones,
-        * and if the initial code point is not in the list, we have to skip
-        * forward to the next element */
-        if (i == -1 || ! ELEMENT_RANGE_MATCHES_INVLIST(i)) {
-            i++;
-            if (i >= len) { /* Finished if beyond the end of the array */
-                return;
-            }
-            current = array[i];
-           if (current >= end) {   /* Finished if beyond the end of what we
-                                      are populating */
-                if (LIKELY(end < UV_MAX)) {
-                    return;
-                }
-
-                /* We get here when the upper bound is the maximum
-                 * representable on the machine, and we are looking for just
-                 * that code point.  Have to special case it */
-                i = len;
-                goto join_end_of_list;
-            }
-        }
-        assert(current >= start);
-
-       /* The current range ends one below the next one, except don't go past
-        * <end> */
-        i++;
-        upper = (i < len && array[i] < end) ? array[i] : end;
-
-       /* Here we are in a range that matches.  Populate a bit in the 3-bit U8
-        * for each code point in it */
-        for (; current < upper; current++) {
-            const STRLEN offset = (STRLEN)(current - start);
-            swatch[offset >> 3] |= 1 << (offset & 7);
-        }
-
-      join_end_of_list:
-
-       /* Quit if at the end of the list */
-        if (i >= len) {
-
-           /* But first, have to deal with the highest possible code point on
-            * the platform.  The previous code assumes that <end> is one
-            * beyond where we want to populate, but that is impossible at the
-            * platform's infinity, so have to handle it specially */
-            if (UNLIKELY(end == UV_MAX && ELEMENT_RANGE_MATCHES_INVLIST(len-1)))
-           {
-                const STRLEN offset = (STRLEN)(end - start);
-                swatch[offset >> 3] |= 1 << (offset & 7);
-            }
-            return;
-        }
-
-       /* Advance to the next range, which will be for code points not in the
-        * inversion list */
-        current = array[i];
-    }
-
-    return;
-}
-
-void
 Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b,
                                          const bool complement_b, SV** output)
 {
@@ -10261,18 +10279,15 @@ Perl__invlist_invert(pTHX_ SV* const invlist)
 SV*
 Perl_invlist_clone(pTHX_ SV* const invlist, SV* new_invlist)
 {
-
     /* Return a new inversion list that is a copy of the input one, which is
      * unchanged.  The new list will not be mortal even if the old one was. */
 
-    const STRLEN nominal_length = _invlist_len(invlist);    /* Why not +1 XXX */
+    const STRLEN nominal_length = _invlist_len(invlist);
     const STRLEN physical_length = SvCUR(invlist);
     const bool offset = *(get_invlist_offset_addr(invlist));
 
     PERL_ARGS_ASSERT_INVLIST_CLONE;
 
-    /* Need to allocate extra space to accommodate Perl's addition of a
-     * trailing NUL to SvPV's, since it thinks they are always strings */
     if (new_invlist == NULL) {
         new_invlist = _new_invlist(nominal_length);
     }
@@ -10563,7 +10578,8 @@ Perl__invlistEQ(pTHX_ SV* const a, SV* const b, const bool complement_b)
 
 /*
  * As best we can, determine the characters that can match the start of
- * the given EXACTF-ish node.
+ * the given EXACTF-ish node.  This is for use in creating ssc nodes, so there
+ * can be false positive matches
  *
  * Returns the invlist as a new SV*; it is the caller's responsibility to
  * call SvREFCNT_dec() when done with it.
@@ -10571,6 +10587,7 @@ Perl__invlistEQ(pTHX_ SV* const a, SV* const b, const bool complement_b)
 STATIC SV*
 S__make_exactf_invlist(pTHX_ RExC_state_t *pRExC_state, regnode *node)
 {
+    dVAR;
     const U8 * s = (U8*)STRING(node);
     SSize_t bytelen = STR_LEN(node);
     UV uc;
@@ -10595,9 +10612,14 @@ S__make_exactf_invlist(pTHX_ RExC_state_t *pRExC_state, regnode *node)
         }
         else {
             /* Any Latin1 range character can potentially match any
-             * other depending on the locale */
+             * other depending on the locale, and in Turkic locales, U+130 and
+             * U+131 */
             if (OP(node) == EXACTFL) {
                 _invlist_union(invlist, PL_Latin1, &invlist);
+                invlist = add_cp_to_invlist(invlist,
+                                                LATIN_SMALL_LETTER_DOTLESS_I);
+                invlist = add_cp_to_invlist(invlist,
+                                        LATIN_CAPITAL_LETTER_I_WITH_DOT_ABOVE);
             }
             else {
                 /* But otherwise, it matches at least itself.  We can
@@ -10701,6 +10723,26 @@ S__make_exactf_invlist(pTHX_ RExC_state_t *pRExC_state, regnode *node)
 
                 invlist = add_cp_to_invlist(invlist, c);
             }
+
+            if (OP(node) == EXACTFL) {
+
+                /* If either [iI] are present in an EXACTFL node the above code
+                 * should have added its normal case pair, but under a Turkish
+                 * locale they could match instead the case pairs from it.  Add
+                 * those as potential matches as well */
+                if (isALPHA_FOLD_EQ(fc, 'I')) {
+                    invlist = add_cp_to_invlist(invlist,
+                                                LATIN_SMALL_LETTER_DOTLESS_I);
+                    invlist = add_cp_to_invlist(invlist,
+                                        LATIN_CAPITAL_LETTER_I_WITH_DOT_ABOVE);
+                }
+                else if (fc == LATIN_SMALL_LETTER_DOTLESS_I) {
+                    invlist = add_cp_to_invlist(invlist, 'I');
+                }
+                else if (fc == LATIN_CAPITAL_LETTER_I_WITH_DOT_ABOVE) {
+                    invlist = add_cp_to_invlist(invlist, 'i');
+                }
+            }
         }
     }
 
@@ -10913,7 +10955,7 @@ S_parse_lparen_question_flags(pTHX_ RExC_state_t *pRExC_state)
                 return;
             default:
               fail_modifiers:
-                RExC_parse += SKIP_IF_CHAR(RExC_parse);
+                RExC_parse += SKIP_IF_CHAR(RExC_parse, RExC_end);
                /* diag_listed_as: Sequence (?%s...) not recognized in regex; marked by <-- HERE in m/%s/ */
                 vFAIL2utf8f("Sequence (%" UTF8f "...) not recognized",
                       UTF8fARG(UTF, RExC_parse-seqstart, seqstart));
@@ -10970,14 +11012,14 @@ S_handle_named_backref(pTHX_ RExC_state_t *pRExC_state,
     RExC_sawback = 1;
     ret = reganode(pRExC_state,
                    ((! FOLD)
-                     ? NREF
+                     ? REFN
                      : (ASCII_FOLD_RESTRICTED)
-                       ? NREFFA
+                       ? REFFAN
                        : (AT_LEAST_UNI_SEMANTICS)
-                         ? NREFFU
+                         ? REFFUN
                          : (LOC)
-                           ? NREFFL
-                           : NREFF),
+                           ? REFFLN
+                           : REFFN),
                     num);
     *flagp |= HASWIDTH;
 
@@ -11016,6 +11058,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
     I32 freeze_paren = 0;
     I32 after_freeze = 0;
     I32 num; /* numeric backreferences */
+    SV * max_open;  /* Max number of unclosed parens */
 
     char * parse_start = RExC_parse; /* MJD */
     char * const oregcomp_parse = RExC_parse;
@@ -11025,8 +11068,26 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
     PERL_ARGS_ASSERT_REG;
     DEBUG_PARSE("reg ");
 
+
+    max_open = get_sv(RE_COMPILE_RECURSION_LIMIT, GV_ADD);
+    assert(max_open);
+    if (!SvIOK(max_open)) {
+        sv_setiv(max_open, RE_COMPILE_RECURSION_INIT);
+    }
+    if (depth > 4 * (UV) SvIV(max_open)) { /* We increase depth by 4 for each
+                                              open paren */
+        vFAIL("Too many nested open parens");
+    }
+
     *flagp = 0;                                /* Tentatively. */
 
+    if (RExC_in_lookbehind) {
+       RExC_in_lookbehind++;
+    }
+    if (RExC_in_lookahead) {
+        RExC_in_lookahead++;
+    }
+
     /* Having this true makes it feasible to have a lot fewer tests for the
      * parse pointer being in scope.  For example, we can write
      *      while(isFOO(*RExC_parse)) RExC_parse++;
@@ -11313,7 +11374,9 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
 
            } /* End of switch */
            if ( ! op ) {
-               RExC_parse += UTF ? UTF8SKIP(RExC_parse) : 1;
+               RExC_parse += UTF
+                              ? UTF8_SAFE_SKIP(RExC_parse, RExC_end)
+                              : 1;
                 if (has_upper || verb_len == 0) {
                     vFAIL2utf8f(
                     "Unknown verb pattern '%" UTF8f "'",
@@ -11393,7 +11456,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
                     return handle_named_backref(pRExC_state, flagp,
                                                 parse_start, ')');
                 }
-                RExC_parse += SKIP_IF_CHAR(RExC_parse);
+                RExC_parse += SKIP_IF_CHAR(RExC_parse, RExC_end);
                 /* diag_listed_as: Sequence (?%s...) not recognized in regex; marked by <-- HERE in m/%s/ */
                vFAIL3("Sequence (%.*s...) not recognized",
                                 RExC_parse-seqstart, seqstart);
@@ -11489,10 +11552,11 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
                 if (RExC_parse >= RExC_end) {
                     vFAIL("Sequence (?... not terminated");
                 }
-
-                /* FALLTHROUGH */
+                RExC_seen_zerolen++;
+                break;
            case '=':           /* (?=...) */
                RExC_seen_zerolen++;
+                RExC_in_lookahead++;
                 break;
            case '!':           /* (?!...) */
                RExC_seen_zerolen++;
@@ -11551,14 +11615,14 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
                 goto gen_recurse_regop;
                 /* NOTREACHED */
             case '+':
-                if (!(RExC_parse[0] >= '1' && RExC_parse[0] <= '9')) {
+                if (! inRANGE(RExC_parse[0], '1', '9')) {
                     RExC_parse++;
                     vFAIL("Illegal pattern");
                 }
                 goto parse_recursion;
                 /* NOTREACHED*/
             case '-': /* (?-1) */
-                if (!(RExC_parse[0] >= '1' && RExC_parse[0] <= '9')) {
+                if (! inRANGE(RExC_parse[0], '1', '9')) {
                     RExC_parse--; /* rewind to let it be handled later */
                     goto parse_flags;
                 }
@@ -11610,7 +11674,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
                         /* It might be a forward reference; we can't fail until
                          * we know, by completing the parse to get all the
                          * groups, and then reparsing */
-                        if (RExC_total_parens > 0)  {
+                        if (ALL_PARENS_COUNTED)  {
                             RExC_parse++;
                             vFAIL("Reference to nonexistent group");
                         }
@@ -11636,7 +11700,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
                     /* It might be a forward reference; we can't fail until we
                      * know, by completing the parse to get all the groups, and
                      * then reparsing */
-                    if (RExC_total_parens > 0)  {
+                    if (ALL_PARENS_COUNTED)  {
                         if (num >= RExC_total_parens) {
                             RExC_parse++;
                             vFAIL("Reference to nonexistent group");
@@ -11668,7 +11732,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
            case '?':           /* (??...) */
                is_logical = 1;
                if (*RExC_parse != '{') {
-                    RExC_parse += SKIP_IF_CHAR(RExC_parse);
+                    RExC_parse += SKIP_IF_CHAR(RExC_parse, RExC_end);
                     /* diag_listed_as: Sequence (?%s...) not recognized in regex; marked by <-- HERE in m/%s/ */
                     vFAIL2utf8f(
                         "Sequence (%" UTF8f "...) not recognized",
@@ -11804,7 +11868,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
                         RExC_rxi->data->data[num]=(void*)sv_dat;
                         SvREFCNT_inc_simple_void_NN(sv_dat);
                     }
-                    ret = reganode(pRExC_state, NGROUPP, num);
+                    ret = reganode(pRExC_state, GROUPPN, num);
                     goto insert_if_check_paren;
                }
                else if (memBEGINs(RExC_parse,
@@ -11827,7 +11891,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
                         parno = 1;
                         RExC_parse++;
                     }
-                    else if (RExC_parse[0] >= '1' && RExC_parse[0] <= '9' ) {
+                    else if (inRANGE(RExC_parse[0], '1', '9')) {
                         UV uv;
                         endptr = RExC_end;
                         if (grok_atoUV(RExC_parse, &uv, &endptr)
@@ -11848,7 +11912,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
                    ret = reganode(pRExC_state, INSUBP, parno);
                    goto insert_if_check_paren;
                }
-               else if (RExC_parse[0] >= '1' && RExC_parse[0] <= '9' ) {
+                else if (inRANGE(RExC_parse[0], '1', '9')) {
                     /* (?(1)...) */
                    char c;
                     UV uv;
@@ -11866,7 +11930,9 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
 
                  insert_if_check_paren:
                    if (UCHARAT(RExC_parse) != ')') {
-                        RExC_parse += UTF ? UTF8SKIP(RExC_parse) : 1;
+                        RExC_parse += UTF
+                                      ? UTF8_SAFE_SKIP(RExC_parse, RExC_end)
+                                      : 1;
                        vFAIL("Switch condition not recognized");
                    }
                    nextchar(pRExC_state);
@@ -11928,7 +11994,9 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
 #endif
                    return ret;
                }
-                RExC_parse += UTF ? UTF8SKIP(RExC_parse) : 1;
+                RExC_parse += UTF
+                              ? UTF8_SAFE_SKIP(RExC_parse, RExC_end)
+                              : 1;
                 vFAIL("Unknown switch condition (?(...))");
            }
            case '[':           /* (?[ ... ]) */
@@ -11938,6 +12006,12 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
                RExC_parse--; /* for vFAIL to print correctly */
                 vFAIL("Sequence (? incomplete");
                 break;
+
+            case ')':
+                if (RExC_strict) {  /* [perl #132851] */
+                    ckWARNreg(RExC_parse, "Empty (?) without any modifiers");
+                }
+                /* FALLTHROUGH */
            default: /* e.g., (?i) */
                RExC_parse = (char *) seqstart + 1;
               parse_flags:
@@ -11967,34 +12041,47 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
          capturing_parens:
            parno = RExC_npar;
            RExC_npar++;
-            if (RExC_total_parens <= 0) {
+            if (! ALL_PARENS_COUNTED) {
                 /* If we are in our first pass through (and maybe only pass),
                  * we  need to allocate memory for the capturing parentheses
-                 * data structures.  Since we start at npar=1, when it reaches
-                 * 2, for the first time it has something to put in it.  Above
-                 * 2 means we extend what we already have */
-                if (RExC_npar == 2) {
+                 * data structures.
+                 */
+
+                if (!RExC_parens_buf_size) {
+                    /* first guess at number of parens we might encounter */
+                    RExC_parens_buf_size = 10;
+
                     /* setup RExC_open_parens, which holds the address of each
                      * OPEN tag, and to make things simpler for the 0 index the
                      * start of the program - this is used later for offsets */
-                    Newxz(RExC_open_parens, RExC_npar, regnode_offset);
+                    Newxz(RExC_open_parens, RExC_parens_buf_size,
+                            regnode_offset);
                     RExC_open_parens[0] = 1;    /* +1 for REG_MAGIC */
 
                     /* setup RExC_close_parens, which holds the address of each
                      * CLOSE tag, and to make things simpler for the 0 index
                      * the end of the program - this is used later for offsets
                      * */
-                    Newxz(RExC_close_parens, RExC_npar, regnode_offset);
+                    Newxz(RExC_close_parens, RExC_parens_buf_size,
+                            regnode_offset);
                     /* we dont know where end op starts yet, so we dont need to
                      * set RExC_close_parens[0] like we do RExC_open_parens[0]
                      * above */
                 }
-                else {
-                    Renew(RExC_open_parens, RExC_npar, regnode_offset);
-                    Zero(RExC_open_parens + RExC_npar - 1, 1, regnode_offset);
+                else if (RExC_npar > RExC_parens_buf_size) {
+                    I32 old_size = RExC_parens_buf_size;
+
+                    RExC_parens_buf_size *= 2;
 
-                    Renew(RExC_close_parens, RExC_npar, regnode_offset);
-                    Zero(RExC_close_parens + RExC_npar - 1, 1, regnode_offset);
+                    Renew(RExC_open_parens, RExC_parens_buf_size,
+                            regnode_offset);
+                    Zero(RExC_open_parens + old_size,
+                            RExC_parens_buf_size - old_size, regnode_offset);
+
+                    Renew(RExC_close_parens, RExC_parens_buf_size,
+                            regnode_offset);
+                    Zero(RExC_close_parens + old_size,
+                            RExC_parens_buf_size - old_size, regnode_offset);
                 }
             }
 
@@ -12006,7 +12093,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
                 DEBUG_OPTIMISE_MORE_r(Perl_re_printf( aTHX_
                     "%*s%*s Setting open paren #%" IVdf " to %d\n",
                     22, "|    |", (int)(depth * 2 + 1), "",
-                    (IV)parno, REG_NODE_NUM(REGNODE_p(ret))));
+                    (IV)parno, ret));
                 RExC_open_parens[parno]= ret;
             }
 
@@ -12076,7 +12163,9 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
             RETURN_FAIL_ON_RESTART(flags, flagp);
             FAIL2("panic: regbranch returned failure, flags=%#" UVxf, (UV) flags);
         }
-        REGTAIL(pRExC_state, lastbr, br);               /* BRANCH -> BRANCH. */
+        if (!  REGTAIL(pRExC_state, lastbr, br)) {  /* BRANCH -> BRANCH. */
+            REQUIRE_BRANCHJ(flagp, 0);
+        }
        lastbr = br;
        *flagp |= flags & (SPSTART | HASWIDTH | POSTPONED);
     }
@@ -12095,7 +12184,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
                 DEBUG_OPTIMISE_MORE_r(Perl_re_printf( aTHX_
                         "%*s%*s Setting close paren #%" IVdf " to %d\n",
                         22, "|    |", (int)(depth * 2 + 1), "",
-                        (IV)parno, REG_NODE_NUM(REGNODE_p(ender))));
+                        (IV)parno, ender));
                 RExC_close_parens[parno]= ender;
                if (RExC_nestroot == parno)
                    RExC_nestroot = 0;
@@ -12129,7 +12218,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
                 DEBUG_OPTIMISE_MORE_r(Perl_re_printf( aTHX_
                     "%*s%*s Setting close paren #0 (END) to %d\n",
                     22, "|    |", (int)(depth * 2 + 1), "",
-                    REG_NODE_NUM(REGNODE_p(ender))));
+                    ender));
 
                 RExC_close_parens[0]= ender;
             }
@@ -12141,13 +12230,15 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
             regprop(RExC_rx, RExC_mysv2, REGNODE_p(ender), NULL, pRExC_state);
             Perl_re_printf( aTHX_  "~ tying lastbr %s (%" IVdf ") to ender %s (%" IVdf ") offset %" IVdf "\n",
                           SvPV_nolen_const(RExC_mysv1),
-                          (IV)REG_NODE_NUM(REGNODE_p(lastbr)),
+                          (IV)lastbr,
                           SvPV_nolen_const(RExC_mysv2),
-                          (IV)REG_NODE_NUM(REGNODE_p(ender)),
+                          (IV)ender,
                           (IV)(ender - lastbr)
             );
         );
-        REGTAIL(pRExC_state, lastbr, ender);
+        if (! REGTAIL(pRExC_state, lastbr, ender)) {
+            REQUIRE_BRANCHJ(flagp, 0);
+        }
 
        if (have_branch) {
             char is_nothing= 1;
@@ -12158,9 +12249,12 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
            for (br = REGNODE_p(ret); br; br = regnext(br)) {
                const U8 op = PL_regkind[OP(br)];
                if (op == BRANCH) {
-                    REGTAIL_STUDY(pRExC_state,
-                                  REGNODE_OFFSET(NEXTOPER(br)),
-                                  ender);
+                    if (! REGTAIL_STUDY(pRExC_state,
+                                        REGNODE_OFFSET(NEXTOPER(br)),
+                                        ender))
+                    {
+                        REQUIRE_BRANCHJ(flagp, 0);
+                    }
                     if ( OP(NEXTOPER(br)) != NOTHING
                          || regnext(NEXTOPER(br)) != REGNODE_p(ender))
                         is_nothing= 0;
@@ -12191,7 +12285,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
                                   SvPV_nolen_const(RExC_mysv1),
                                   (IV)REG_NODE_NUM(ret_as_regnode),
                                   SvPV_nolen_const(RExC_mysv2),
-                                  (IV)REG_NODE_NUM(REGNODE_p(ender)),
+                                  (IV)ender,
                                   (IV)(ender - ret)
                     );
                 );
@@ -12227,7 +12321,10 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
             Set_Node_Cur_Length(REGNODE_p(ret), parse_start);
            Set_Node_Offset(REGNODE_p(ret), parse_start + 1);
            FLAGS(REGNODE_p(ret)) = flag;
-            REGTAIL_STUDY(pRExC_state, ret, reg_node(pRExC_state, TAIL));
+            if (! REGTAIL_STUDY(pRExC_state, ret, reg_node(pRExC_state, TAIL)))
+            {
+                REQUIRE_BRANCHJ(flagp, 0);
+            }
        }
     }
 
@@ -12258,6 +12355,9 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
     if (RExC_in_lookbehind) {
        RExC_in_lookbehind--;
     }
+    if (RExC_in_lookahead) {
+        RExC_in_lookahead--;
+    }
     if (after_freeze > RExC_npar)
         RExC_npar = after_freeze;
     return(ret);
@@ -12321,14 +12421,12 @@ S_regbranch(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, I32 first, U32 depth)
            /* FIXME adding one for every branch after the first is probably
             * excessive now we have TRIE support. (hv) */
            MARK_NAUGHTY(1);
-            if (     chain > (SSize_t) BRANCH_MAX_OFFSET
-                && ! RExC_use_BRANCHJ)
-            {
+            if (! REGTAIL(pRExC_state, chain, latest)) {
                 /* XXX We could just redo this branch, but figuring out what
-                 * bookkeeping needs to be reset is a pain */
+                 * bookkeeping needs to be reset is a pain, and it's likely
+                 * that other branches that goto END will also be too large */
                 REQUIRE_BRANCHJ(flagp, 0);
             }
-            REGTAIL(pRExC_state, chain, latest);
        }
        chain = latest;
        c++;
@@ -12628,20 +12726,23 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
   * points) that this \N sequence matches.  This is set, and the input is
   * parsed for errors, even if the function returns FALSE, as detailed below.
   *
-  * There are 5 possibilities here, as detailed in the next 5 paragraphs.
+  * There are 6 possibilities here, as detailed in the next 6 paragraphs.
   *
   * Probably the most common case is for the \N to specify a single code point.
   * *cp_count will be set to 1, and *code_point_p will be set to that code
   * point.
   *
-  * Another possibility is for the input to be an empty \N{}, which for
-  * backwards compatibility we accept.  *cp_count will be set to 0. *node_p
-  * will be set to a generated NOTHING node.
+  * Another possibility is for the input to be an empty \N{}.  This is no
+  * longer accepted, and will generate a fatal error.
+  *
+  * Another possibility is for a custom charnames handler to be in effect which
+  * translates the input name to an empty string.  *cp_count will be set to 0.
+  * *node_p will be set to a generated NOTHING node.
   *
   * Still another possibility is for the \N to mean [^\n]. *cp_count will be
   * set to 0. *node_p will be set to a generated REG_ANY node.
   *
-  * The fourth possibility is that \N resolves to a sequence of more than one
+  * The fifth possibility is that \N resolves to a sequence of more than one
   * code points.  *cp_count will be set to the number of code points in the
   * sequence. *node_p will be set to a generated node returned by this
   * function calling S_reg().
@@ -12649,7 +12750,7 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
   * The final possibility is that it is premature to be calling this function;
   * the parse needs to be restarted.  This can happen when this changes from
   * /d to /u rules, or when the pattern needs to be upgraded to UTF-8.  The
-  * latter occurs only when the fourth possibility would otherwise be in
+  * latter occurs only when the fifth possibility would otherwise be in
   * effect, and is because one of those code points requires the pattern to be
   * recompiled as UTF-8.  The function returns FALSE, and sets the
   * RESTART_PARSE and NEED_UTF8 flags in *flagp, as appropriate.  When this
@@ -12666,12 +12767,11 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
   * so we need a way to take a snapshot of what they resolve to at the time of
   * the original parse. [perl #56444].
   *
-  * That parsing is skipped for single-quoted regexes, so we may here get
-  * '\N{NAME}'.  This is a fatal error.  These names have to be resolved by the
-  * parser.  But if the single-quoted regex is something like '\N{U+41}', that
-  * is legal and handled here.  The code point is Unicode, and has to be
-  * translated into the native character set for non-ASCII platforms.
-  */
+  * That parsing is skipped for single-quoted regexes, so here we may get
+  * '\N{NAME}', which is parsed now.  If the single-quoted regex is something
+  * like '\N{U+41}', that code point is Unicode, and has to be translated into
+  * the native character set for non-ASCII platforms.  The other possibilities
+  * are already native, so no translation is done. */
 
     char * endbrace;    /* points to '}' following the name */
     char* p = RExC_parse; /* Temporary */
@@ -12680,7 +12780,6 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
     char *orig_end;
     char *save_start;
     I32 flags;
-    Size_t count = 0;   /* code point count kept internally by this function */
 
     GET_RE_DEBUG_FLAGS_DECL;
 
@@ -12703,7 +12802,7 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
 
     /* Disambiguate between \N meaning a named character versus \N meaning
      * [^\n].  The latter is assumed when the {...} following the \N is a legal
-     * quantifier, or there is no '{' at all */
+     * quantifier, or if there is no '{' at all */
     if (*p != '{' || regcurly(p)) {
         RExC_parse = p;
         if (cp_count) {
@@ -12736,15 +12835,19 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
         vFAIL2("Missing right brace on \\%c{}", 'N');
     }
 
-    /* Here, we have decided it should be a named character or sequence */
-    REQUIRE_UNI_RULES(flagp, FALSE); /* Unicode named chars imply Unicode
-                                        semantics */
+    /* Here, we have decided it should be a named character or sequence.  These
+     * imply Unicode semantics */
+    REQUIRE_UNI_RULES(flagp, FALSE);
 
-    if (endbrace == RExC_parse) {   /* empty: \N{} */
+    /* \N{_} is what toke.c returns to us to indicate a name that evaluates to
+     * nothing at all (not allowed under strict) */
+    if (endbrace - RExC_parse == 1 && *RExC_parse == '_') {
+        RExC_parse = endbrace;
         if (strict) {
             RExC_parse++;   /* Position after the "}" */
             vFAIL("Zero length \\N{}");
         }
+
         if (cp_count) {
             *cp_count = 0;
         }
@@ -12757,15 +12860,122 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
         return TRUE;
     }
 
-    /* If we haven't got something that begins with 'U+', then it didn't get lexed. */
-    if (   endbrace - RExC_parse < 2
-        || strnNE(RExC_parse, "U+", 2))
-    {
-        RExC_parse = endbrace;  /* position msg's '<--HERE' */
-        vFAIL("\\N{NAME} must be resolved by the lexer");
-    }
+    if (endbrace - RExC_parse < 2 || ! strBEGINs(RExC_parse, "U+")) {
 
-        /* This code purposely indented below because of future changes coming */
+        /* Here, the name isn't of the form  U+....  This can happen if the
+         * pattern is single-quoted, so didn't get evaluated in toke.c.  Now
+         * is the time to find out what the name means */
+
+        const STRLEN name_len = endbrace - RExC_parse;
+        SV *  value_sv;     /* What does this name evaluate to */
+        SV ** value_svp;
+        const U8 * value;   /* string of name's value */
+        STRLEN value_len;   /* and its length */
+
+        /*  RExC_unlexed_names is a hash of names that weren't evaluated by
+         *  toke.c, and their values. Make sure is initialized */
+        if (! RExC_unlexed_names) {
+            RExC_unlexed_names = newHV();
+        }
+
+        /* If we have already seen this name in this pattern, use that.  This
+         * allows us to only call the charnames handler once per name per
+         * pattern.  A broken or malicious handler could return something
+         * different each time, which could cause the results to vary depending
+         * on if something gets added or subtracted from the pattern that
+         * causes the number of passes to change, for example */
+        if ((value_svp = hv_fetch(RExC_unlexed_names, RExC_parse,
+                                                      name_len, 0)))
+        {
+            value_sv = *value_svp;
+        }
+        else { /* Otherwise we have to go out and get the name */
+            const char * error_msg = NULL;
+            value_sv = get_and_check_backslash_N_name(RExC_parse, endbrace,
+                                                      UTF,
+                                                      &error_msg);
+            if (error_msg) {
+                RExC_parse = endbrace;
+                vFAIL(error_msg);
+            }
+
+            /* If no error message, should have gotten a valid return */
+            assert (value_sv);
+
+            /* Save the name's meaning for later use */
+            if (! hv_store(RExC_unlexed_names, RExC_parse, name_len,
+                           value_sv, 0))
+            {
+                Perl_croak(aTHX_ "panic: hv_store() unexpectedly failed");
+            }
+        }
+
+        /* Here, we have the value the name evaluates to in 'value_sv' */
+        value = (U8 *) SvPV(value_sv, value_len);
+
+        /* See if the result is one code point vs 0 or multiple */
+        if (value_len > 0 && value_len <= (UV) ((SvUTF8(value_sv))
+                                               ? UTF8SKIP(value)
+                                               : 1))
+        {
+            /* Here, exactly one code point.  If that isn't what is wanted,
+             * fail */
+            if (! code_point_p) {
+                RExC_parse = p;
+                return FALSE;
+            }
+
+            /* Convert from string to numeric code point */
+            *code_point_p = (SvUTF8(value_sv))
+                            ? valid_utf8_to_uvchr(value, NULL)
+                            : *value;
+
+            /* Have parsed this entire single code point \N{...}.  *cp_count
+             * has already been set to 1, so don't do it again. */
+            RExC_parse = endbrace;
+            nextchar(pRExC_state);
+            return TRUE;
+        } /* End of is a single code point */
+
+        /* Count the code points, if caller desires.  The API says to do this
+         * even if we will later return FALSE */
+        if (cp_count) {
+            *cp_count = 0;
+
+            *cp_count = (SvUTF8(value_sv))
+                        ? utf8_length(value, value + value_len)
+                        : value_len;
+        }
+
+        /* Fail if caller doesn't want to handle a multi-code-point sequence.
+         * But don't back the pointer up if the caller wants to know how many
+         * code points there are (they need to handle it themselves in this
+         * case).  */
+        if (! node_p) {
+            if (! cp_count) {
+                RExC_parse = p;
+            }
+            return FALSE;
+        }
+
+        /* Convert this to a sub-pattern of the form "(?: ... )", and then call
+         * reg recursively to parse it.  That way, it retains its atomicness,
+         * while not having to worry about any special handling that some code
+         * points may have. */
+
+        substitute_parse = newSVpvs("?:");
+        sv_catsv(substitute_parse, value_sv);
+        sv_catpv(substitute_parse, ")");
+
+#ifdef EBCDIC
+        /* The value should already be native, so no need to convert on EBCDIC
+         * platforms.*/
+        assert(! RExC_recode_x_to_native);
+#endif
+
+    }
+    else {   /* \N{U+...} */
+        Size_t count = 0;   /* code point count kept internally */
 
         /* We can get to here when the input is \N{U+...} or when toke.c has
          * converted a name to the \N{U+...} form.  This include changing a
@@ -12900,6 +13110,8 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
         RExC_recode_x_to_native = 1;
 #endif
 
+    }
+
     /* Here, we have the string the name evaluates to, ready to be parsed,
      * stored in 'substitute_parse' as a series of valid "\x{...}\x{...}"
      * constructs.  This can be called from within a substitute parse already.
@@ -13096,6 +13308,7 @@ S_backref_value(char *p, char *e)
 STATIC regnode_offset
 S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
 {
+    dVAR;
     regnode_offset ret = 0;
     I32 flags = 0;
     char *parse_start;
@@ -13230,15 +13443,21 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
            *flagp |= SIMPLE;
            goto finish_meta_pat;
        case 'K':
-           RExC_seen_zerolen++;
-           ret = reg_node(pRExC_state, KEEPS);
-           *flagp |= SIMPLE;
-           /* XXX:dmq : disabling in-place substitution seems to
-            * be necessary here to avoid cases of memory corruption, as
-            * with: C<$_="x" x 80; s/x\K/y/> -- rgs
-            */
-            RExC_seen |= REG_LOOKBEHIND_SEEN;
-           goto finish_meta_pat;
+            if (!RExC_in_lookbehind && !RExC_in_lookahead) {
+                RExC_seen_zerolen++;
+                ret = reg_node(pRExC_state, KEEPS);
+                *flagp |= SIMPLE;
+                /* XXX:dmq : disabling in-place substitution seems to
+                 * be necessary here to avoid cases of memory corruption, as
+                 * with: C<$_="x" x 80; s/x\K/y/> -- rgs
+                 */
+                RExC_seen |= REG_LOOKBEHIND_SEEN;
+                goto finish_meta_pat;
+            }
+            else {
+                ++RExC_parse; /* advance past the 'K' */
+                vFAIL("\\K not permitted in lookahead/lookbehind");
+            }
        case 'Z':
            ret = reg_node(pRExC_state, SEOL);
            *flagp |= SIMPLE;
@@ -13268,25 +13487,17 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
             /* FALLTHROUGH */
        case 'b':
           {
+            U8 flags = 0;
            regex_charset charset = get_regex_charset(RExC_flags);
 
            RExC_seen_zerolen++;
             RExC_seen |= REG_LOOKBEHIND_SEEN;
            op = BOUND + charset;
 
-            if (op == BOUND) {
-                RExC_seen_d_op = TRUE;
-            }
-            else if (op == BOUNDL) {
-                RExC_contains_locale = 1;
-            }
-
-           ret = reg_node(pRExC_state, op);
-           *flagp |= SIMPLE;
            if (RExC_parse >= RExC_end || *(RExC_parse + 1) != '{') {
-                FLAGS(REGNODE_p(ret)) = TRADITIONAL_BOUND;
+                flags = TRADITIONAL_BOUND;
                 if (op > BOUNDA) {  /* /aa is same as /a */
-                    OP(REGNODE_p(ret)) = BOUNDA;
+                    op = BOUNDA;
                 }
             }
             else {
@@ -13294,9 +13505,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                 char name = *RExC_parse;
                 char * endbrace = NULL;
                 RExC_parse += 2;
-                if (RExC_parse < RExC_end) {
-                    endbrace = (char *) memchr(RExC_parse, '}', RExC_end - RExC_parse);
-                }
+                endbrace = (char *) memchr(RExC_parse, '}', RExC_end - RExC_parse);
 
                 if (! endbrace) {
                     vFAIL2("Missing right brace on \\%c{}", name);
@@ -13322,25 +13531,25 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                         {
                             goto bad_bound_type;
                         }
-                        FLAGS(REGNODE_p(ret)) = GCB_BOUND;
+                        flags = GCB_BOUND;
                         break;
                     case 'l':
                         if (length != 2 || *(RExC_parse + 1) != 'b') {
                             goto bad_bound_type;
                         }
-                        FLAGS(REGNODE_p(ret)) = LB_BOUND;
+                        flags = LB_BOUND;
                         break;
                     case 's':
                         if (length != 2 || *(RExC_parse + 1) != 'b') {
                             goto bad_bound_type;
                         }
-                        FLAGS(REGNODE_p(ret)) = SB_BOUND;
+                        flags = SB_BOUND;
                         break;
                     case 'w':
                         if (length != 2 || *(RExC_parse + 1) != 'b') {
                             goto bad_bound_type;
                         }
-                        FLAGS(REGNODE_p(ret)) = WB_BOUND;
+                        flags = WB_BOUND;
                         break;
                     default:
                       bad_bound_type:
@@ -13353,8 +13562,11 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                 RExC_parse = endbrace;
                 REQUIRE_UNI_RULES(flagp, 0);
 
-                if (op >= BOUNDA) {  /* /aa is same as /a */
-                    OP(REGNODE_p(ret)) = BOUNDU;
+                if (op == BOUND) {
+                    op = BOUNDU;
+                }
+                else if (op >= BOUNDA) {  /* /aa is same as /a */
+                    op = BOUNDU;
                     length += 4;
 
                     /* Don't have to worry about UTF-8, in this message because
@@ -13369,9 +13581,22 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                 }
            }
 
+            if (op == BOUND) {
+                RExC_seen_d_op = TRUE;
+            }
+            else if (op == BOUNDL) {
+                RExC_contains_locale = 1;
+            }
+
             if (invert) {
-                OP(REGNODE_p(ret)) += NBOUND - BOUND;
+                op += NBOUND - BOUND;
             }
+
+           ret = reg_node(pRExC_state, op);
+            FLAGS(REGNODE_p(ret)) = flags;
+
+           *flagp |= SIMPLE;
+
            goto finish_meta_pat;
           }
 
@@ -13596,7 +13821,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                         && num >= RExC_npar
                         /* cannot be an octal escape if it starts with 8 */
                         && *RExC_parse != '8'
-                        /* cannot be an octal escape it it starts with 9 */
+                        /* cannot be an octal escape if it starts with 9 */
                         && *RExC_parse != '9'
                     ) {
                         /* Probably not meant to be a backref, instead likely
@@ -13625,7 +13850,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                     /* It might be a forward reference; we can't fail until we
                      * know, by completing the parse to get all the groups, and
                      * then reparsing */
-                    if (RExC_total_parens > 0)  {
+                    if (ALL_PARENS_COUNTED)  {
                         if (num >= RExC_total_parens)  {
                             vFAIL("Reference to nonexistent group");
                         }
@@ -13727,7 +13952,8 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
             /* We can convert EXACTF nodes to EXACTFU if they contain only
              * characters that match identically regardless of the target
              * string's UTF8ness.  The reason to do this is that EXACTF is not
-             * trie-able, EXACTFU is.
+             * trie-able, EXACTFU is, and EXACTFU requires fewer operations at
+             * runtime.
              *
              * Similarly, we can convert EXACTFL nodes to EXACTFLU8 if they
              * contain only above-Latin1 characters (hence must be in UTF8),
@@ -13776,7 +14002,6 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                    || UTF8_IS_INVARIANT(UCHARAT(RExC_parse))
                    || UTF8_IS_START(UCHARAT(RExC_parse)));
 
-
             /* Here, we have a literal character.  Find the maximal string of
              * them in the input that we can fit into a single EXACTish node.
              * We quit at the first non-literal or when the node gets full, or
@@ -14151,7 +14376,8 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                         goto loopdone;
                     }
 
-                    /* This code point means we can't simplify things */
+                    /* This problematic code point means we can't simplify
+                     * things */
                     maybe_exactfu = FALSE;
 
                     /* Here, we are adding a problematic fold character.
@@ -14277,18 +14503,16 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                             has_micro_sign = TRUE;
                         }
 
-                        *(s++) = (char) (DEPENDS_SEMANTICS)
-                                        ? toFOLD(ender)
-
-                                          /* Under /u, the fold of any
-                                           * character in the 0-255 range
-                                           * happens to be its lowercase
-                                           * equivalent, except for LATIN SMALL
-                                           * LETTER SHARP S, which was handled
-                                           * above, and the MICRO SIGN, whose
-                                           * fold requires UTF-8 to represent.
-                                           * */
-                                        : toLOWER_L1(ender);
+                        *(s++) = (DEPENDS_SEMANTICS)
+                                 ? (char) toFOLD(ender)
+
+                                   /* Under /u, the fold of any character in
+                                    * the 0-255 range happens to be its
+                                    * lowercase equivalent, except for LATIN
+                                    * SMALL LETTER SHARP S, which was handled
+                                    * above, and the MICRO SIGN, whose fold
+                                    * requires UTF-8 to represent.  */
+                                 : (char) toLOWER_L1(ender);
                     }
                } /* End of adding current character to the node */
 
@@ -14326,14 +14550,15 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
              * identifies, so when it is set to less than the full node, we can
              * skip the rest of this */
             if (FOLD && p < RExC_end && upper_parse == MAX_NODE_STRING_SIZE) {
+                PERL_UINT_FAST8_T backup_count = 0;
 
                 const STRLEN full_len = len;
 
                assert(len >= MAX_NODE_STRING_SIZE);
 
-                /* Here, <s> points to the final byte of the final character.
-                 * Look backwards through the string until find a non-
-                 * problematic character */
+                /* Here, <s> points to just beyond where we have output the
+                 * final character of the node.  Look backwards through the
+                 * string until find a non- problematic character */
 
                if (! UTF) {
 
@@ -14342,13 +14567,15 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                         goto loopdone;
                     }
 
-                    while (--s >= s0 && IS_NON_FINAL_FOLD(*s)) { }
+                    while (--s >= s0 && IS_NON_FINAL_FOLD(*s)) {
+                        backup_count++;
+                    }
                     len = s - s0 + 1;
                }
                 else {
 
                     /* Point to the first byte of the final character */
-                    s = (char *) utf8_hop((U8 *) s, -1);
+                    s = (char *) utf8_hop_back((U8 *) s, -1, (U8 *) s0);
 
                     while (s >= s0) {   /* Search backwards until find
                                            a non-problematic char */
@@ -14384,6 +14611,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                          * special case the very first byte in the string, so
                          * we don't read outside the string */
                         s = (s == s0) ? s -1 : (char *) utf8_hop((U8 *) s, -1);
+                        backup_count++;
                     } /* End of loop backwards through the string */
 
                     /* If there were only problematic characters in the string,
@@ -14407,12 +14635,13 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                 } else {
 
                     /* Here, the node does contain some characters that aren't
-                     * problematic.  If one such is the final character in the
-                     * node, we are done */
-                    if (len == full_len) {
+                     * problematic.  If we didn't have to backup any, then the
+                     * final character in the node is non-problematic, and we
+                     * can take the node as-is */
+                    if (backup_count == 0) {
                         goto loopdone;
                     }
-                    else if (len + ((UTF) ? UTF8SKIP(s) : 1) == full_len) {
+                    else if (backup_count == 1) {
 
                         /* If the final character is problematic, but the
                          * penultimate is not, back-off that last character to
@@ -14456,8 +14685,10 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
           loopdone:   /* Jumped to when encounters something that shouldn't be
                          in the node */
 
-            /* Free up any over-allocated space */
-            change_engine_size(pRExC_state, - (initial_size - STR_SZ(len)));
+            /* Free up any over-allocated space; cast is to silence bogus
+             * warning in MS VC */
+            change_engine_size(pRExC_state,
+                                - (Ptrdiff_t) (initial_size - STR_SZ(len)));
 
             /* I (khw) don't know if you can get here with zero length, but the
              * old code handled this situation by creating a zero-length EXACT
@@ -14533,7 +14764,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                 RExC_emit += STR_SZ(len);
 
                 /* If the node isn't a single character, it can't be SIMPLE */
-                if (len > ((UTF) ? UVCHR_SKIP(ender) : 1)) {
+                if (len > (Size_t) ((UTF) ? UVCHR_SKIP(ender) : 1)) {
                     maybe_SIMPLE = 0;
                 }
 
@@ -14579,9 +14810,16 @@ S_populate_ANYOF_from_invlist(pTHX_ regnode *node, SV** invlist_ptr)
      * sets up the bitmap and any flags, removing those code points from the
      * inversion list, setting it to NULL should it become completely empty */
 
+    dVAR;
+
     PERL_ARGS_ASSERT_POPULATE_ANYOF_FROM_INVLIST;
     assert(PL_regkind[OP(node)] == ANYOF);
 
+    /* There is no bitmap for this node type */
+    if (inRANGE(OP(node), ANYOFH, ANYOFHr)) {
+        return;
+    }
+
     ANYOF_BITMAP_ZERO(node);
     if (*invlist_ptr) {
 
@@ -15687,7 +15925,9 @@ redo_curchar:
                             RExC_parse = RExC_end;
                         }
                         else if (RExC_parse != save_parse) {
-                            RExC_parse += (UTF) ? UTF8SKIP(RExC_parse) : 1;
+                            RExC_parse += (UTF)
+                                          ? UTF8_SAFE_SKIP(RExC_parse, RExC_end)
+                                          : 1;
                         }
                         vFAIL("Expecting '(?flags:(?[...'");
                     }
@@ -15749,8 +15989,7 @@ redo_curchar:
                               FALSE, /* Require return to be an ANYOF */
                               &current))
                 {
-                    FAIL2("panic: regclass returned failure to handle_sets, "
-                          "flags=%#" UVxf, (UV) *flagp);
+                    goto regclass_failed;
                 }
 
                 /* regclass() will return with parsing just the \ sequence,
@@ -15786,8 +16025,7 @@ redo_curchar:
                                 FALSE, /* Require return to be an ANYOF */
                                 &current))
                 {
-                    FAIL2("panic: regclass returned failure to handle_sets, "
-                          "flags=%#" UVxf, (UV) *flagp);
+                    goto regclass_failed;
                 }
 
                 if (! current) {
@@ -16148,8 +16386,7 @@ redo_curchar:
     }
 
     if (!node)
-        FAIL2("panic: regclass returned failure to handle_sets, flags=%#" UVxf,
-                    PTR2UV(flagp));
+        goto regclass_failed;
 
     /* Fix up the node type if we are in locale.  (We have pretended we are
      * under /u for the purposes of regclass(), as this construct will only
@@ -16180,6 +16417,10 @@ redo_curchar:
     nextchar(pRExC_state);
     Set_Node_Length(REGNODE_p(node), RExC_parse - oregcomp_parse + 1); /* MJD */
     return node;
+
+  regclass_failed:
+    FAIL2("panic: regclass returned failure to handle_sets, " "flags=%#" UVxf,
+                                                                (UV) *flagp);
 }
 
 #ifdef ENABLE_REGEX_SETS_DEBUGGING
@@ -16430,7 +16671,7 @@ STATIC regnode_offset
 S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                  const bool stop_at_1,  /* Just parse the next thing, don't
                                            look for a full character class */
-                 bool allow_multi_folds,
+                 bool allow_mutiple_chars,
                  const bool silence_non_portable,   /* Don't output warnings
                                                        about too large
                                                        characters */
@@ -16457,7 +16698,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
      *
      * ANYOF nodes contain a bit map for the first NUM_ANYOF_CODE_POINTS
      * characters, with the corresponding bit set if that character is in the
-     * list.  For characters above this, a range list or swash is used.  There
+     * list.  For characters above this, an inversion list is used.  There
      * are extra bits for \w, etc. in locale ANYOFs, as what these match is not
      * determinable at compile time
      *
@@ -16469,15 +16710,16 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
      * UTF-8
      */
 
+    dVAR;
     UV prevvalue = OOB_UNICODE, save_prevvalue = OOB_UNICODE;
     IV range = 0;
     UV value = OOB_UNICODE, save_value = OOB_UNICODE;
-    regnode_offset ret;
+    regnode_offset ret = -1;    /* Initialized to an illegal value */
     STRLEN numlen;
     int namedclass = OOB_NAMEDCLASS;
     char *rangebegin = NULL;
-    bool need_class = 0;
-    SV *listsv = NULL;
+    SV *listsv = NULL;      /* List of \p{user-defined} whose definitions
+                               aren't available at the time this was called */
     STRLEN initial_listsv_len = 0; /* Kind of a kludge to see if it is more
                                      than just initialized.  */
     SV* properties = NULL;    /* Code points that match \p{} \P{} */
@@ -16506,18 +16748,6 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
     const bool skip_white = cBOOL(   ret_invlist
                                   || (RExC_flags & RXf_PMf_EXTENDED_MORE));
 
-    /* Unicode properties are stored in a swash; this holds the current one
-     * being parsed.  If this swash is the only above-latin1 component of the
-     * character class, an optimization is to pass it directly on to the
-     * execution engine.  Otherwise, it is set to NULL to indicate that there
-     * are other things in the class that have to be dealt with at execution
-     * time */
-    SV* swash = NULL;          /* Code points that match \p{} \P{} */
-
-    /* Set if a component of this character class is user-defined; just passed
-     * on to the engine */
-    bool has_user_defined_property = FALSE;
-
     /* inversion list of code points this node matches only when the target
      * string is in UTF-8.  These are all non-ASCII, < 256.  (Because is under
      * /d) */
@@ -16551,7 +16781,6 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
     bool warn_super = ALWAYS_WARN_SUPER;
 
     const char * orig_parse = RExC_parse;
-    bool posixl_matches_all = FALSE; /* Does /l class have both e.g. \W,\w ? */
 
     /* This variable is used to mark where the end in the input is of something
      * that looks like a POSIX construct but isn't.  During the parse, when
@@ -16566,7 +16795,17 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                        one.  */
     U8 anyof_flags = 0;   /* flag bits if the node is an ANYOF-type */
     U32 posixl = 0;       /* bit field of posix classes matched under /l */
-    bool use_anyofd = FALSE; /* ? Is this to be an ANYOFD node */
+
+
+/* Flags as to what things aren't knowable until runtime.  (Note that these are
+ * mutually exclusive.) */
+#define HAS_USER_DEFINED_PROPERTY 0x01   /* /u any user-defined properties that
+                                            haven't been defined as of yet */
+#define HAS_D_RUNTIME_DEPENDENCY  0x02   /* /d if the target being matched is
+                                            UTF-8 or not */
+#define HAS_L_RUNTIME_DEPENDENCY   0x04 /* /l what the posix classes match and
+                                            what gets folded */
+    U32 has_runtime_dependency = 0;     /* OR of the above flags */
 
     GET_RE_DEBUG_FLAGS_DECL;
 
@@ -16587,10 +16826,12 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
 #if UNICODE_MAJOR_VERSION < 3 /* no multifolds in early Unicode */      \
     || (UNICODE_MAJOR_VERSION == 3 && UNICODE_DOT_VERSION == 0          \
                                    && UNICODE_DOT_DOT_VERSION == 0)
-    allow_multi_folds = FALSE;
+    allow_mutiple_chars = FALSE;
 #endif
 
-    listsv = newSVpvs_flags("# comment\n", SVs_TEMP);
+    /* We include the /i status at the beginning of this so that we can
+     * know it at runtime */
+    listsv = sv_2mortal(Perl_newSVpvf(aTHX_ "#%d\n", cBOOL(FOLD)));
     initial_listsv_len = SvCUR(listsv);
     SvTEMP_off(listsv); /* Grr, TEMPs and mortals are conflated.  */
 
@@ -16601,7 +16842,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
     if (UCHARAT(RExC_parse) == '^') {  /* Complement the class */
        RExC_parse++;
         invert = TRUE;
-        allow_multi_folds = FALSE;
+        allow_mutiple_chars = FALSE;
         MARK_NAUGHTY(1);
         SKIP_BRACKETED_WHITE_SPACE(skip_white, RExC_parse);
     }
@@ -16791,11 +17032,16 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                               "Ignoring zero length \\N{} in character class");
                         }
                         else { /* cp_count > 1 */
+                            assert(cp_count > 1);
                             if (! RExC_in_multi_char_class) {
-                                if (invert || range || *RExC_parse == '-') {
+                                if ( ! allow_mutiple_chars
+                                    || invert
+                                    || range
+                                    || *RExC_parse == '-')
+                                {
                                     if (strict) {
                                         RExC_parse--;
-                                        vFAIL("\\N{} in inverted character class or as a range end-point is restricted to one character");
+                                        vFAIL("\\N{} here is restricted to one character");
                                     }
                                     ckWARNreg(RExC_parse, "Using just the first character returned by \\N{} in character class");
                                     break; /* <value> contains the first code
@@ -16829,17 +17075,6 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
            case 'P':
                {
                char *e;
-                char *i;
-
-                /* We will handle any undefined properties ourselves */
-                U8 swash_init_flags = _CORE_SWASH_INIT_RETURN_IF_UNDEF
-                                       /* And we actually would prefer to get
-                                        * the straight inversion list of the
-                                        * swash, since we will be accessing it
-                                        * anyway, to save a little time */
-                                      |_CORE_SWASH_INIT_ACCEPT_INVLIST;
-
-                SvREFCNT_dec(swash); /* Free any left-overs */
 
                /* \p means they want Unicode semantics */
                REQUIRE_UNI_RULES(flagp, 0);
@@ -16884,7 +17119,9 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
 
                }   /* The \p isn't immediately followed by a '{' */
                else if (! isALPHA(*RExC_parse)) {
-                    RExC_parse += (UTF) ? UTF8SKIP(RExC_parse) : 1;
+                    RExC_parse += (UTF)
+                                  ? UTF8_SAFE_SKIP(RExC_parse, RExC_end)
+                                  : 1;
                     vFAIL2("Character following \\%c must be '{' or a "
                            "single-character Unicode property name",
                            (U8) value);
@@ -16895,169 +17132,88 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                }
                {
                     char* name = RExC_parse;
-                    char* base_name;    /* name after any packages are stripped */
-                    char* lookup_name = NULL;
-                    const char * const colon_colon = "::";
-                    bool invert;
-
-                    SV* invlist;
-
-                    /* Temporary workaround for [perl #133136].  For this
-                    * precise input that is in the .t that is failing, load
-                    * utf8.pm, which is what the test wants, so that that
-                    * .t passes */
-                    if (     memEQs(RExC_start, e + 1 - RExC_start,
-                                    "foo\\p{Alnum}")
-                        && ! hv_common(GvHVn(PL_incgv),
-                                       NULL,
-                                       "utf8.pm", sizeof("utf8.pm") - 1,
-                                       0, HV_FETCH_ISEXISTS, NULL, 0))
-                    {
-                        require_pv("utf8.pm");
-                    }
-                    invlist = parse_uniprop_string(name, n, FOLD, &invert);
-                    if (invlist) {
-                        if (invert) {
-                            value ^= 'P' ^ 'p';
-                        }
-                    }
-                    else {
 
-                    /* Try to get the definition of the property into
-                     * <invlist>.  If /i is in effect, the effective property
-                     * will have its name be <__NAME_i>.  The design is
-                     * discussed in commit
-                     * 2f833f5208e26b208886e51e09e2c072b5eabb46 */
-                    name = savepv(Perl_form(aTHX_ "%.*s", (int)n, RExC_parse));
-                    SAVEFREEPV(name);
-
-                    for (i = RExC_parse; i < RExC_parse + n; i++) {
-                        if (isCNTRL(*i) && *i != '\t') {
-                            RExC_parse = e + 1;
-                            vFAIL2("Can't find Unicode property definition \"%s\"", name);
+                    /* Any message returned about expanding the definition */
+                    SV* msg = newSVpvs_flags("", SVs_TEMP);
+
+                    /* If set TRUE, the property is user-defined as opposed to
+                     * official Unicode */
+                    bool user_defined = FALSE;
+
+                    SV * prop_definition = parse_uniprop_string(
+                                            name, n, UTF, FOLD,
+                                            FALSE, /* This is compile-time */
+
+                                            /* We can't defer this defn when
+                                             * the full result is required in
+                                             * this call */
+                                            ! cBOOL(ret_invlist),
+
+                                            &user_defined,
+                                            msg,
+                                            0 /* Base level */
+                                           );
+                    if (SvCUR(msg)) {   /* Assumes any error causes a msg */
+                        assert(prop_definition == NULL);
+                        RExC_parse = e + 1;
+                        if (SvUTF8(msg)) {  /* msg being UTF-8 makes the whole
+                                               thing so, or else the display is
+                                               mojibake */
+                            RExC_utf8 = TRUE;
                         }
+                       /* diag_listed_as: Can't find Unicode property definition "%s" in regex; marked by <-- HERE in m/%s/ */
+                        vFAIL2utf8f("%" UTF8f, UTF8fARG(SvUTF8(msg),
+                                    SvCUR(msg), SvPVX(msg)));
                     }
 
-                    if (FOLD) {
-                        lookup_name = savepv(Perl_form(aTHX_ "__%s_i", name));
-
-                        /* The function call just below that uses this can fail
-                         * to return, leaking memory if we don't do this */
-                        SAVEFREEPV(lookup_name);
-                    }
-
-                    /* Look up the property name, and get its swash and
-                     * inversion list, if the property is found  */
-                    swash = _core_swash_init("utf8",
-                                             (lookup_name)
-                                              ? lookup_name
-                                              : name,
-                                             &PL_sv_undef,
-                                             1, /* binary */
-                                             0, /* not tr/// */
-                                             NULL, /* No inversion list */
-                                             &swash_init_flags
-                                            );
-                    if (! swash || ! (invlist = _get_swash_invlist(swash))) {
-                        HV* curpkg = (IN_PERL_COMPILETIME)
-                                      ? PL_curstash
-                                      : CopSTASH(PL_curcop);
-                        UV final_n = n;
-                        bool has_pkg;
-
-                        if (swash) {    /* Got a swash but no inversion list.
-                                           Something is likely wrong that will
-                                           be sorted-out later */
-                            SvREFCNT_dec_NN(swash);
-                            swash = NULL;
-                        }
+                    if (! is_invlist(prop_definition)) {
 
-                        /* Here didn't find it.  It could be a an error (like a
-                         * typo) in specifying a Unicode property, or it could
-                         * be a user-defined property that will be available at
-                         * run-time.  The names of these must begin with 'In'
-                         * or 'Is' (after any packages are stripped off).  So
-                         * if not one of those, or if we accept only
-                         * compile-time properties, is an error; otherwise add
-                         * it to the list for run-time look up. */
-                        if ((base_name = rninstr(name, name + n,
-                                                 colon_colon, colon_colon + 2)))
-                        { /* Has ::.  We know this must be a user-defined
-                             property */
-                            base_name += 2;
-                            final_n -= base_name - name;
-                            has_pkg = TRUE;
+                        /* Here, the definition isn't known, so we have gotten
+                         * returned a string that will be evaluated if and when
+                         * encountered at runtime.  We add it to the list of
+                         * such properties, along with whether it should be
+                         * complemented or not */
+                        if (value == 'P') {
+                            sv_catpvs(listsv, "!");
                         }
                         else {
-                            base_name = name;
-                            has_pkg = FALSE;
-                        }
-
-                        if (   final_n < 3
-                            || base_name[0] != 'I'
-                            || (base_name[1] != 's' && base_name[1] != 'n')
-                            || ret_invlist)
-                        {
-                            const char * const msg
-                                = (has_pkg)
-                                  ? "Illegal user-defined property name"
-                                  : "Can't find Unicode property definition";
-                            RExC_parse = e + 1;
-
-                            /* diag_listed_as: Can't find Unicode property definition "%s" */
-                            vFAIL3utf8f("%s \"%" UTF8f "\"",
-                                msg, UTF8fARG(UTF, n, name));
+                            sv_catpvs(listsv, "+");
                         }
+                        sv_catsv(listsv, prop_definition);
 
-                        /* If the property name doesn't already have a package
-                         * name, add the current one to it so that it can be
-                         * referred to outside it. [perl #121777] */
-                        if (! has_pkg && curpkg) {
-                            char* pkgname = HvNAME(curpkg);
-                            if (memNEs(pkgname, HvNAMELEN(curpkg), "main")) {
-                                char* full_name = Perl_form(aTHX_
-                                                            "%s::%s",
-                                                            pkgname,
-                                                            name);
-                                n = strlen(full_name);
-                                name = savepvn(full_name, n);
-                                SAVEFREEPV(name);
-                            }
-                        }
-                        Perl_sv_catpvf(aTHX_ listsv, "%cutf8::%s%" UTF8f "%s\n",
-                                        (value == 'p' ? '+' : '!'),
-                                        (FOLD) ? "__" : "",
-                                        UTF8fARG(UTF, n, name),
-                                        (FOLD) ? "_i" : "");
-                        has_user_defined_property = TRUE;
-                        optimizable = FALSE;    /* Will have to leave this an
-                                                   ANYOF node */
+                        has_runtime_dependency |= HAS_USER_DEFINED_PROPERTY;
 
                         /* We don't know yet what this matches, so have to flag
                          * it */
                         anyof_flags |= ANYOF_SHARED_d_UPPER_LATIN1_UTF8_STRING_MATCHES_non_d_RUNTIME_USER_PROP;
                     }
                     else {
+                        assert (prop_definition && is_invlist(prop_definition));
 
-                        /* Here, did get the swash and its inversion list.  If
-                         * the swash is from a user-defined property, then this
-                         * whole character class should be regarded as such */
-                        if (swash_init_flags
-                            & _CORE_SWASH_INIT_USER_DEFINED_PROPERTY)
+                        /* Here we do have the complete property definition
+                         *
+                         * Temporary workaround for [perl #133136].  For this
+                         * precise input that is in the .t that is failing,
+                         * load utf8.pm, which is what the test wants, so that
+                         * that .t passes */
+                        if (     memEQs(RExC_start, e + 1 - RExC_start,
+                                        "foo\\p{Alnum}")
+                            && ! hv_common(GvHVn(PL_incgv),
+                                           NULL,
+                                           "utf8.pm", sizeof("utf8.pm") - 1,
+                                           0, HV_FETCH_ISEXISTS, NULL, 0))
                         {
-                            has_user_defined_property = TRUE;
+                            require_pv("utf8.pm");
                         }
-                    }
-                    }
-                    if (invlist) {
-                        if (! has_user_defined_property &&
+
+                        if (! user_defined &&
                             /* We warn on matching an above-Unicode code point
                              * if the match would return true, except don't
                              * warn for \p{All}, which has exactly one element
                              * = 0 */
-                            (_invlist_contains_cp(invlist, 0x110000)
-                                && (! (_invlist_len(invlist) == 1
-                                       && *invlist_array(invlist) == 0))))
+                            (_invlist_contains_cp(prop_definition, 0x110000)
+                                && (! (_invlist_len(prop_definition) == 1
+                                       && *invlist_array(prop_definition) == 0))))
                         {
                             warn_super = TRUE;
                         }
@@ -17065,23 +17221,11 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                         /* Invert if asking for the complement */
                         if (value == 'P') {
                            _invlist_union_complement_2nd(properties,
-                                                          invlist,
+                                                          prop_definition,
                                                           &properties);
-
-                            /* The swash can't be used as-is, because we've
-                            * inverted things; delay removing it to here after
-                            * have copied its invlist above */
-                            if (! swash) {
-                                SvREFCNT_dec_NN(invlist);
-                            }
-                            SvREFCNT_dec(swash);
-                            swash = NULL;
                         }
                         else {
-                            _invlist_union(properties, invlist, &properties);
-                            if (! swash) {
-                                SvREFCNT_dec_NN(invlist);
-                            }
+                            _invlist_union(properties, prop_definition, &properties);
                        }
                     }
                 }
@@ -17152,7 +17296,9 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                    RExC_parse += numlen;
                     if (numlen != 3) {
                         if (strict) {
-                            RExC_parse += (UTF) ? UTF8SKIP(RExC_parse) : 1;
+                            RExC_parse += (UTF)
+                                          ? UTF8_SAFE_SKIP(RExC_parse, RExC_end)
+                                          : 1;
                             vFAIL("Need exactly 3 octal digits");
                         }
                         else if (   numlen < 3 /* like \08, \178 */
@@ -17224,75 +17370,67 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
             ) {
                 SV* scratch_list = NULL;
 
-                /* What the Posix classes (like \w, [:space:]) match in locale
-                 * isn't knowable under locale until actual match time.  Room
-                 * must be reserved (one time per outer bracketed class) to
-                 * store such classes.  The space will contain a bit for each
-                 * named class that is to be matched against.  This isn't
-                 * needed for \p{} and pseudo-classes, as they are not affected
-                 * by locale, and hence are dealt with separately */
-                if (! need_class) {
-                    need_class = 1;
+                /* What the Posix classes (like \w, [:space:]) match isn't
+                 * generally knowable under locale until actual match time.  A
+                 * special node is used for these which has extra space for a
+                 * bitmap, with a bit reserved for each named class that is to
+                 * be matched against.  (This isn't needed for \p{} and
+                 * pseudo-classes, as they are not affected by locale, and
+                 * hence are dealt with separately.)  However, if a named class
+                 * and its complement are both present, then it matches
+                 * everything, and there is no runtime dependency.  Odd numbers
+                 * are the complements of the next lower number, so xor works.
+                 * (Note that something like [\w\D] should match everything,
+                 * because \d should be a proper subset of \w.  But rather than
+                 * trust that the locale is well behaved, we leave this to
+                 * runtime to sort out) */
+                if (POSIXL_TEST(posixl, namedclass ^ 1)) {
+                    cp_list = _add_range_to_invlist(cp_list, 0, UV_MAX);
+                    POSIXL_ZERO(posixl);
+                    has_runtime_dependency &= ~HAS_L_RUNTIME_DEPENDENCY;
+                    anyof_flags &= ~ANYOF_MATCHES_POSIXL;
+                    continue;   /* We could ignore the rest of the class, but
+                                   best to parse it for any errors */
+                }
+                else { /* Here, isn't the complement of any already parsed
+                          class */
+                    POSIXL_SET(posixl, namedclass);
+                    has_runtime_dependency |= HAS_L_RUNTIME_DEPENDENCY;
                     anyof_flags |= ANYOF_MATCHES_POSIXL;
 
-                    /* We can't change this into some other type of node
-                     * (unless this is the only element, in which case there
-                     * are nodes that mean exactly this) as has runtime
-                     * dependencies */
-                    optimizable = FALSE;
-                }
-
-                /* Coverity thinks it is possible for this to be negative; both
-                 * jhi and khw think it's not, but be safer */
-                assert(! (anyof_flags & ANYOF_MATCHES_POSIXL)
-                       || (namedclass + ((namedclass % 2) ? -1 : 1)) >= 0);
-
-                /* See if it already matches the complement of this POSIX
-                 * class */
-                if (  (anyof_flags & ANYOF_MATCHES_POSIXL)
-                    && POSIXL_TEST(posixl, namedclass + ((namedclass % 2)
-                                                         ? -1
-                                                         : 1)))
-                {
-                    posixl_matches_all = TRUE;
-                    break;  /* No need to continue.  Since it matches both
-                               e.g., \w and \W, it matches everything, and the
-                               bracketed class can be optimized into qr/./s */
+                    /* The above-Latin1 characters are not subject to locale
+                     * rules.  Just add them to the unconditionally-matched
+                     * list */
+
+                    /* Get the list of the above-Latin1 code points this
+                     * matches */
+                    _invlist_intersection_maybe_complement_2nd(PL_AboveLatin1,
+                                            PL_XPosix_ptrs[classnum],
+
+                                            /* Odd numbers are complements,
+                                             * like NDIGIT, NASCII, ... */
+                                            namedclass % 2 != 0,
+                                            &scratch_list);
+                    /* Checking if 'cp_list' is NULL first saves an extra
+                     * clone.  Its reference count will be decremented at the
+                     * next union, etc, or if this is the only instance, at the
+                     * end of the routine */
+                    if (! cp_list) {
+                        cp_list = scratch_list;
+                    }
+                    else {
+                        _invlist_union(cp_list, scratch_list, &cp_list);
+                        SvREFCNT_dec_NN(scratch_list);
+                    }
+                    continue;   /* Go get next character */
                 }
+            }
+            else {
 
-                /* Add this class to those that should be checked at runtime */
-                POSIXL_SET(posixl, namedclass);
-
-                /* The above-Latin1 characters are not subject to locale rules.
-                 * Just add them to the unconditionally-matched list */
-
-                /* Get the list of the above-Latin1 code points this matches */
-                _invlist_intersection_maybe_complement_2nd(PL_AboveLatin1,
-                                        PL_XPosix_ptrs[classnum],
-
-                                        /* Odd numbers are complements, like
-                                        * NDIGIT, NASCII, ... */
-                                        namedclass % 2 != 0,
-                                        &scratch_list);
-                /* Checking if 'cp_list' is NULL first saves an extra clone.
-                 * Its reference count will be decremented at the next union,
-                 * etc, or if this is the only instance, at the end of the
-                 * routine */
-                if (! cp_list) {
-                    cp_list = scratch_list;
-                }
-                else {
-                    _invlist_union(cp_list, scratch_list, &cp_list);
-                    SvREFCNT_dec_NN(scratch_list);
-                }
-                continue;   /* Go get next character */
-            }
-            else {
-
-                /* Here, is not /l, or is a POSIX class for which /l doesn't
-                 * matter (or is a Unicode property, which is skipped here). */
-                if (namedclass >= ANYOF_POSIXL_MAX) {  /* If a special class */
-                    if (namedclass != ANYOF_UNIPROP) { /* UNIPROP = \p and \P */
+                /* Here, is not /l, or is a POSIX class for which /l doesn't
+                 * matter (or is a Unicode property, which is skipped here). */
+                if (namedclass >= ANYOF_POSIXL_MAX) {  /* If a special class */
+                    if (namedclass != ANYOF_UNIPROP) { /* UNIPROP = \p and \P */
 
                         /* Here, should be \h, \H, \v, or \V.  None of /d, /i
                          * nor /l make a difference in what these match,
@@ -17447,8 +17585,8 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
          *  "ss"  =~ /^[^\xDF]+$/i => N
          *
          * See [perl #89750] */
-        if (FOLD && allow_multi_folds && value == prevvalue) {
-            if (value == LATIN_SMALL_LETTER_SHARP_S
+        if (FOLD && allow_mutiple_chars && value == prevvalue) {
+            if (    value == LATIN_SMALL_LETTER_SHARP_S
                 || (value > 255 && _invlist_contains_cp(PL_HasMultiCharFold,
                                                         value)))
             {
@@ -17621,7 +17759,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                            literal
                         );
                 }
-                else if isMNEMONIC_CNTRL(value) {
+                else if (isMNEMONIC_CNTRL(value)) {
                     vWARN4(RExC_parse,
                            "\"%.*s\" is more clearly written simply as \"%s\"",
                            (int) (RExC_parse - rangebegin),
@@ -17790,8 +17928,10 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
 
             /* Our calculated list will be for Unicode rules.  For locale
              * matching, we have to keep a separate list that is consulted at
-             * runtime only when the locale indicates Unicode rules.  For
-             * non-locale, we just use the general list */
+             * runtime only when the locale indicates Unicode rules (and we
+             * don't include potential matches in the ASCII/Latin1 range, as
+             * any code point could fold to any other, based on the run-time
+             * locale).   For non-locale, we just use the general list */
             if (LOC) {
                 use_list = &only_utf8_locale_list;
             }
@@ -17823,7 +17963,16 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
 
                     if (j < 256) {
 
-                        if (IS_IN_SOME_FOLD_L1(j)) {
+                        /* Under /l, we don't know what code points below 256
+                         * fold to, except we do know the MICRO SIGN folds to
+                         * an above-255 character if the locale is UTF-8, so we
+                         * add it to the special list (in *use_list)  Otherwise
+                         * we know now what things can match, though some folds
+                         * are valid under /d only if the target is UTF-8.
+                         * Those go in a separate list */
+                        if (      IS_IN_SOME_FOLD_L1(j)
+                            && ! (LOC && j != MICRO_SIGN))
+                        {
 
                             /* ASCII is always matched; non-ASCII is matched
                              * only under Unicode rules (which could happen
@@ -17914,8 +18063,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
 
     /* And combine the result (if any) with any inversion lists from posix
      * classes.  The lists are kept separate up to now because we don't want to
-     * fold the classes (folding of those is automatically handled by the swash
-     * fetching code) */
+     * fold the classes */
     if (simple_posixes) {   /* These are the classes known to be unaffected by
                                /a, /aa, and /d */
         if (cp_list) {
@@ -17955,7 +18103,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
              * the target string is in UTF-8.  But things like \W match all the
              * upper Latin1 characters if the target string is not in UTF-8.
              *
-             * Handle the case where there something like \W separately */
+             * Handle the case with something like \W separately */
             if (nposixes) {
                 SV* only_non_utf8_list = invlist_clone(PL_UpperLatin1, NULL);
 
@@ -18029,9 +18177,9 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
 
                 SvREFCNT_dec(nonascii_but_latin1_properties);
 
-                /* Get rid of any characters that we now know are matched
-                 * unconditionally from the conditional list, which may make
-                 * that list empty */
+                /* Get rid of any characters from the conditional list that we
+                 * now know are matched unconditionally, which may make that
+                 * list empty */
                 _invlist_subtract(upper_latin1_only_utf8_matches,
                                   cp_list,
                                   &upper_latin1_only_utf8_matches);
@@ -18096,10 +18244,9 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
      * folded until runtime */
 
     /* If we didn't do folding, it's because some information isn't available
-     * until runtime; set the run-time fold flag for these.  (We don't have to
-     * worry about properties folding, as that is taken care of by the swash
-     * fetching).  We know to set the flag if we have a non-NULL list for UTF-8
-     * locales, or the class matches at least one 0-255 range code point */
+     * until runtime; set the run-time fold flag for these  We know to set the
+     * flag if we have a non-NULL list for UTF-8 locales, or the class matches
+     * at least one 0-255 range code point */
     if (LOC && FOLD) {
 
         /* Some things on the list might be unconditionally included because of
@@ -18114,7 +18261,11 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                 only_utf8_locale_list = NULL;
             }
         }
-        if (only_utf8_locale_list) {
+        if (    only_utf8_locale_list
+            || (cp_list && (   _invlist_contains_cp(cp_list, LATIN_CAPITAL_LETTER_I_WITH_DOT_ABOVE)
+                            || _invlist_contains_cp(cp_list, LATIN_SMALL_LETTER_DOTLESS_I))))
+        {
+            has_runtime_dependency |= HAS_L_RUNTIME_DEPENDENCY;
             anyof_flags
                  |= ANYOFL_FOLD
                  |  ANYOFL_SHARED_UTF8_LOCALE_fold_HAS_MATCHES_nonfold_REQD;
@@ -18124,6 +18275,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
             invlist_iterinit(cp_list);
             if (invlist_iternext(cp_list, &start, &end) && start < 256) {
                 anyof_flags |= ANYOFL_FOLD;
+                has_runtime_dependency |= HAS_L_RUNTIME_DEPENDENCY;
             }
             invlist_iterfinish(cp_list);
         }
@@ -18132,36 +18284,24 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
              && (    upper_latin1_only_utf8_matches
                  || (anyof_flags & ANYOF_SHARED_d_MATCHES_ALL_NON_UTF8_NON_ASCII_non_d_WARN_SUPER)))
     {
-        use_anyofd = TRUE;
         RExC_seen_d_op = TRUE;
-        optimizable = FALSE;
+        has_runtime_dependency |= HAS_D_RUNTIME_DEPENDENCY;
     }
 
-    /* Optimize inverted simple patterns (e.g. [^a-z]) when everything is known
-     * at compile time.  Besides not inverting folded locale now, we can't
-     * invert if there are things such as \w, which aren't known until runtime
-     * */
+    /* Optimize inverted patterns (e.g. [^a-z]) when everything is known at
+     * compile time. */
     if (     cp_list
         &&   invert
-        && ! use_anyofd
-        && ! (anyof_flags & (ANYOF_LOCALE_FLAGS))
-       && ! HAS_NONLOCALE_RUNTIME_PROPERTY_DEFINITION)
+        && ! has_runtime_dependency)
     {
         _invlist_invert(cp_list);
 
-        /* Any swash can't be used as-is, because we've inverted things */
-        if (swash) {
-            SvREFCNT_dec_NN(swash);
-            swash = NULL;
-        }
-
        /* Clear the invert flag since have just done it here */
        invert = FALSE;
     }
 
     if (ret_invlist) {
         *ret_invlist = cp_list;
-        SvREFCNT_dec(swash);
 
         return RExC_emit;
     }
@@ -18171,105 +18311,492 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
      * routine) */
     *flagp |= HASWIDTH|SIMPLE;
 
+    if (anyof_flags & ANYOF_LOCALE_FLAGS) {
+        RExC_contains_locale = 1;
+    }
+
     /* Some character classes are equivalent to other nodes.  Such nodes take
-     * up less room and generally fewer operations to execute than ANYOF nodes.
-     * */
+     * up less room, and some nodes require fewer operations to execute, than
+     * ANYOF nodes.  EXACTish nodes may be joinable with adjacent nodes to
+     * improve efficiency. */
 
     if (optimizable) {
-        int posix_class = -1;   /* Illegal value */
-        UV start, end;
+        PERL_UINT_FAST8_T i;
+        Size_t partial_cp_count = 0;
+        UV start[MAX_FOLD_FROMS+1] = { 0 }; /* +1 for the folded-to char */
+        UV   end[MAX_FOLD_FROMS+1] = { 0 };
 
-        if (UNLIKELY(posixl_matches_all)) {
-            ret = reg_node(pRExC_state, SANY);
-            goto not_anyof;
-        }
+        if (cp_list) { /* Count the code points in enough ranges that we would
+                          see all the ones possible in any fold in this version
+                          of Unicode */
 
-        if (cp_list && ! invert) {
             invlist_iterinit(cp_list);
-            if (! invlist_iternext(cp_list, &start, &end)) {
+            for (i = 0; i <= MAX_FOLD_FROMS; i++) {
+                if (! invlist_iternext(cp_list, &start[i], &end[i])) {
+                    break;
+                }
+                partial_cp_count += end[i] - start[i] + 1;
+            }
+
+            invlist_iterfinish(cp_list);
+        }
 
-                /* Here, the list is empty.  This happens, for example, when a
-                 * Unicode property that doesn't match anything is the only
-                 * element in the character class (perluniprops.pod notes such
-                 * properties).  */
+        /* If we know at compile time that this matches every possible code
+         * point, any run-time dependencies don't matter */
+        if (start[0] == 0 && end[0] == UV_MAX) {
+            if (invert) {
                 ret = reganode(pRExC_state, OPFAIL, 0);
+            }
+            else {
+                ret = reg_node(pRExC_state, SANY);
+                MARK_NAUGHTY(1);
+            }
+            goto not_anyof;
+        }
+
+        /* Similarly, for /l posix classes, if both a class and its
+         * complement match, any run-time dependencies don't matter */
+        if (posixl) {
+            for (namedclass = 0; namedclass < ANYOF_POSIXL_MAX;
+                                                        namedclass += 2)
+            {
+                if (   POSIXL_TEST(posixl, namedclass)      /* class */
+                    && POSIXL_TEST(posixl, namedclass + 1)) /* its complement */
+                {
+                    if (invert) {
+                        ret = reganode(pRExC_state, OPFAIL, 0);
+                    }
+                    else {
+                        ret = reg_node(pRExC_state, SANY);
+                        MARK_NAUGHTY(1);
+                    }
+                    goto not_anyof;
+                }
+            }
+            /* For well-behaved locales, some classes are subsets of others,
+             * so complementing the subset and including the non-complemented
+             * superset should match everything, like [\D[:alnum:]], and
+             * [[:^alpha:][:alnum:]], but some implementations of locales are
+             * buggy, and khw thinks its a bad idea to have optimization change
+             * behavior, even if it avoids an OS bug in a given case */
+
+#define isSINGLE_BIT_SET(n) isPOWER_OF_2(n)
+
+            /* If is a single posix /l class, can optimize to just that op.
+             * Such a node will not match anything in the Latin1 range, as that
+             * is not determinable until runtime, but will match whatever the
+             * class does outside that range.  (Note that some classes won't
+             * match anything outside the range, like [:ascii:]) */
+            if (    isSINGLE_BIT_SET(posixl)
+                && (partial_cp_count == 0 || start[0] > 255))
+            {
+                U8 classnum;
+                SV * class_above_latin1 = NULL;
+                bool already_inverted;
+                bool are_equivalent;
+
+                /* Compute which bit is set, which is the same thing as, e.g.,
+                 * ANYOF_CNTRL.  From
+                 * https://graphics.stanford.edu/~seander/bithacks.html#IntegerLogDeBruijn
+                 * */
+                static const int MultiplyDeBruijnBitPosition2[32] =
+                    {
+                    0, 1, 28, 2, 29, 14, 24, 3, 30, 22, 20, 15, 25, 17, 4, 8,
+                    31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9
+                    };
+
+                namedclass = MultiplyDeBruijnBitPosition2[(posixl
+                                                          * 0x077CB531U) >> 27];
+                classnum = namedclass_to_classnum(namedclass);
+
+                /* The named classes are such that the inverted number is one
+                 * larger than the non-inverted one */
+                already_inverted = namedclass
+                                 - classnum_to_namedclass(classnum);
+
+                /* Create an inversion list of the official property, inverted
+                 * if the constructed node list is inverted, and restricted to
+                 * only the above latin1 code points, which are the only ones
+                 * known at compile time */
+                _invlist_intersection_maybe_complement_2nd(
+                                                    PL_AboveLatin1,
+                                                    PL_XPosix_ptrs[classnum],
+                                                    already_inverted,
+                                                    &class_above_latin1);
+                are_equivalent = _invlistEQ(class_above_latin1, cp_list,
+                                                                        FALSE);
+                SvREFCNT_dec_NN(class_above_latin1);
+
+                if (are_equivalent) {
+
+                    /* Resolve the run-time inversion flag with this possibly
+                     * inverted class */
+                    invert = invert ^ already_inverted;
+
+                    ret = reg_node(pRExC_state,
+                                   POSIXL + invert * (NPOSIXL - POSIXL));
+                    FLAGS(REGNODE_p(ret)) = classnum;
+                    goto not_anyof;
+                }
+            }
+        }
+
+        /* khw can't think of any other possible transformation involving
+         * these. */
+        if (has_runtime_dependency & HAS_USER_DEFINED_PROPERTY) {
+            goto is_anyof;
+        }
+
+        if (! has_runtime_dependency) {
+
+            /* If the list is empty, nothing matches.  This happens, for
+             * example, when a Unicode property that doesn't match anything is
+             * the only element in the character class (perluniprops.pod notes
+             * such properties). */
+            if (partial_cp_count == 0) {
+                if (invert) {
+                    ret = reg_node(pRExC_state, SANY);
+                }
+                else {
+                    ret = reganode(pRExC_state, OPFAIL, 0);
+                }
+
+                goto not_anyof;
+            }
+
+            /* If matches everything but \n */
+            if (   start[0] == 0 && end[0] == '\n' - 1
+                && start[1] == '\n' + 1 && end[1] == UV_MAX)
+            {
+                assert (! invert);
+                ret = reg_node(pRExC_state, REG_ANY);
+                MARK_NAUGHTY(1);
                 goto not_anyof;
             }
+        }
 
-            if (start == end) {    /* The range is a single code point */
-                if (! invlist_iternext(cp_list, &start, &end)
+        /* Next see if can optimize classes that contain just a few code points
+         * into an EXACTish node.  The reason to do this is to let the
+         * optimizer join this node with adjacent EXACTish ones.
+         *
+         * An EXACTFish node can be generated even if not under /i, and vice
+         * versa.  But care must be taken.  An EXACTFish node has to be such
+         * that it only matches precisely the code points in the class, but we
+         * want to generate the least restrictive one that does that, to
+         * increase the odds of being able to join with an adjacent node.  For
+         * example, if the class contains [kK], we have to make it an EXACTFAA
+         * node to prevent the KELVIN SIGN from matching.  Whether we are under
+         * /i or not is irrelevant in this case.  Less obvious is the pattern
+         * qr/[\x{02BC}]n/i.  U+02BC is MODIFIER LETTER APOSTROPHE. That is
+         * supposed to match the single character U+0149 LATIN SMALL LETTER N
+         * PRECEDED BY APOSTROPHE.  And so even though there is no simple fold
+         * that includes \X{02BC}, there is a multi-char fold that does, and so
+         * the node generated for it must be an EXACTFish one.  On the other
+         * hand qr/:/i should generate a plain EXACT node since the colon
+         * participates in no fold whatsoever, and having it EXACT tells the
+         * optimizer the target string cannot match unless it has a colon in
+         * it.
+         *
+         * We don't typically generate an EXACTish node if doing so would
+         * require changing the pattern to UTF-8, as that affects /d and
+         * otherwise is slower.  However, under /i, not changing to UTF-8 can
+         * miss some potential multi-character folds.  We calculate the
+         * EXACTish node, and then decide if something would be missed if we
+         * don't upgrade */
+        if (   ! posixl
+            && ! invert
+
+                /* Only try if there are no more code points in the class than
+                 * in the max possible fold */
+            &&   partial_cp_count > 0 && partial_cp_count <= MAX_FOLD_FROMS + 1
+
+            && (start[0] < 256 || UTF || FOLD))
+        {
+            if (partial_cp_count == 1 && ! upper_latin1_only_utf8_matches)
+            {
+                /* We can always make a single code point class into an
+                 * EXACTish node. */
+
+                if (LOC) {
+
+                    /* Here is /l:  Use EXACTL, except /li indicates EXACTFL,
+                     * as that means there is a fold not known until runtime so
+                     * shows as only a single code point here. */
+                    op = (FOLD) ? EXACTFL : EXACTL;
+                }
+                else if (! FOLD) { /* Not /l and not /i */
+                    op = (start[0] < 256) ? EXACT : EXACT_ONLY8;
+                }
+                else if (start[0] < 256) { /* /i, not /l, and the code point is
+                                              small */
+
+                    /* Under /i, it gets a little tricky.  A code point that
+                     * doesn't participate in a fold should be an EXACT node.
+                     * We know this one isn't the result of a simple fold, or
+                     * there'd be more than one code point in the list, but it
+                     * could be part of a multi- character fold.  In that case
+                     * we better not create an EXACT node, as we would wrongly
+                     * be telling the optimizer that this code point must be in
+                     * the target string, and that is wrong.  This is because
+                     * if the sequence around this code point forms a
+                     * multi-char fold, what needs to be in the string could be
+                     * the code point that folds to the sequence.
+                     *
+                     * This handles the case of below-255 code points, as we
+                     * have an easy look up for those.  The next clause handles
+                     * the above-256 one */
+                    op = IS_IN_SOME_FOLD_L1(start[0])
+                         ? EXACTFU
+                         : EXACT;
+                }
+                else {  /* /i, larger code point.  Since we are under /i, and
+                           have just this code point, we know that it can't
+                           fold to something else, so PL_InMultiCharFold
+                           applies to it */
+                    op = _invlist_contains_cp(PL_InMultiCharFold,
+                                              start[0])
+                         ? EXACTFU_ONLY8
+                         : EXACT_ONLY8;
+                }
+
+                value = start[0];
+            }
+            else if (  ! (has_runtime_dependency & ~HAS_D_RUNTIME_DEPENDENCY)
+                     && _invlist_contains_cp(PL_in_some_fold, start[0]))
+            {
+                /* Here, the only runtime dependency, if any, is from /d, and
+                 * the class matches more than one code point, and the lowest
+                 * code point participates in some fold.  It might be that the
+                 * other code points are /i equivalent to this one, and hence
+                 * they would representable by an EXACTFish node.  Above, we
+                 * eliminated classes that contain too many code points to be
+                 * EXACTFish, with the test for MAX_FOLD_FROMS
+                 *
+                 * First, special case the ASCII fold pairs, like 'B' and 'b'.
+                 * We do this because we have EXACTFAA at our disposal for the
+                 * ASCII range */
+                if (partial_cp_count == 2 && isASCII(start[0])) {
+
+                    /* The only ASCII characters that participate in folds are
+                     * alphabetics */
+                    assert(isALPHA(start[0]));
+                    if (   end[0] == start[0]   /* First range is a single
+                                                   character, so 2nd exists */
+                        && isALPHA_FOLD_EQ(start[0], start[1]))
+                    {
 
-                        /* Don't do this optimization if it would require
-                         * changing the pattern to UTF-8 */
-                    && (start < 256 || UTF))
-                {
-                    /* Here, the list contains a single code point.  Can
-                     * optimize into an EXACTish node */
+                        /* Here, is part of an ASCII fold pair */
 
-                    value = start;
+                        if (   ASCII_FOLD_RESTRICTED
+                            || HAS_NONLATIN1_SIMPLE_FOLD_CLOSURE(start[0]))
+                        {
+                            /* If the second clause just above was true, it
+                             * means we can't be under /i, or else the list
+                             * would have included more than this fold pair.
+                             * Therefore we have to exclude the possibility of
+                             * whatever else it is that folds to these, by
+                             * using EXACTFAA */
+                            op = EXACTFAA;
+                        }
+                        else if (HAS_NONLATIN1_FOLD_CLOSURE(start[0])) {
 
-                    if (! FOLD) {
-                        op = (LOC)
-                             ? EXACTL
-                             : EXACT;
-                    }
-                    else if (LOC) {
+                            /* Here, there's no simple fold that start[0] is part
+                             * of, but there is a multi-character one.  If we
+                             * are not under /i, we want to exclude that
+                             * possibility; if under /i, we want to include it
+                             * */
+                            op = (FOLD) ? EXACTFU : EXACTFAA;
+                        }
+                        else {
+
+                            /* Here, the only possible fold start[0] particpates in
+                             * is with start[1].  /i or not isn't relevant */
+                            op = EXACTFU;
+                        }
 
-                        /* A locale node under folding with one code point can
-                         * be an EXACTFL, as its fold won't be calculated until
-                         * runtime */
-                        op = EXACTFL;
+                        value = toFOLD(start[0]);
+                    }
+                }
+                else if (  ! upper_latin1_only_utf8_matches
+                         || (   _invlist_len(upper_latin1_only_utf8_matches)
+                                                                          == 2
+                             && PL_fold_latin1[
+                               invlist_highest(upper_latin1_only_utf8_matches)]
+                             == start[0]))
+                {
+                    /* Here, the smallest character is non-ascii or there are
+                     * more than 2 code points matched by this node.  Also, we
+                     * either don't have /d UTF-8 dependent matches, or if we
+                     * do, they look like they could be a single character that
+                     * is the fold of the lowest one in the always-match list.
+                     * This test quickly excludes most of the false positives
+                     * when there are /d UTF-8 depdendent matches.  These are
+                     * like LATIN CAPITAL LETTER A WITH GRAVE matching LATIN
+                     * SMALL LETTER A WITH GRAVE iff the target string is
+                     * UTF-8.  (We don't have to worry above about exceeding
+                     * the array bounds of PL_fold_latin1[] because any code
+                     * point in 'upper_latin1_only_utf8_matches' is below 256.)
+                     *
+                     * EXACTFAA would apply only to pairs (hence exactly 2 code
+                     * points) in the ASCII range, so we can't use it here to
+                     * artificially restrict the fold domain, so we check if
+                     * the class does or does not match some EXACTFish node.
+                     * Further, if we aren't under /i, and and the folded-to
+                     * character is part of a multi-character fold, we can't do
+                     * this optimization, as the sequence around it could be
+                     * that multi-character fold, and we don't here know the
+                     * context, so we have to assume it is that multi-char
+                     * fold, to prevent potential bugs.
+                     *
+                     * To do the general case, we first find the fold of the
+                     * lowest code point (which may be higher than the lowest
+                     * one), then find everything that folds to it.  (The data
+                     * structure we have only maps from the folded code points,
+                     * so we have to do the earlier step.) */
+
+                    Size_t foldlen;
+                    U8 foldbuf[UTF8_MAXBYTES_CASE];
+                    UV folded = _to_uni_fold_flags(start[0],
+                                                        foldbuf, &foldlen, 0);
+                    unsigned int first_fold;
+                    const unsigned int * remaining_folds;
+                    Size_t folds_to_this_cp_count = _inverse_folds(
+                                                            folded,
+                                                            &first_fold,
+                                                            &remaining_folds);
+                    Size_t folds_count = folds_to_this_cp_count + 1;
+                    SV * fold_list = _new_invlist(folds_count);
+                    unsigned int i;
+
+                    /* If there are UTF-8 dependent matches, create a temporary
+                     * list of what this node matches, including them. */
+                    SV * all_cp_list = NULL;
+                    SV ** use_this_list = &cp_list;
+
+                    if (upper_latin1_only_utf8_matches) {
+                        all_cp_list = _new_invlist(0);
+                        use_this_list = &all_cp_list;
+                        _invlist_union(cp_list,
+                                       upper_latin1_only_utf8_matches,
+                                       use_this_list);
                     }
-                    else {
 
-                        /* Here, we are generally folding, but there is only
-                         * one code point to match.  If we have to, we use an
-                         * EXACT node, but it would be better for joining with
-                         * adjacent nodes in the optimization phase if we used
-                         * the same EXACTFish node that any such are likely to
-                         * be.  We can do this iff the code point doesn't
-                         * participate in any folds.  For example, an EXACTF of
-                         * a colon is the same as an EXACT one, since nothing
-                         * folds to or from a colon. */
-                        if (value < 256) {
-                            if (IS_IN_SOME_FOLD_L1(value)) {
-                                op = EXACT;
-                            }
+                    /* Having gotten everything that participates in the fold
+                     * containing the lowest code point, we turn that into an
+                     * inversion list, making sure everything is included. */
+                    fold_list = add_cp_to_invlist(fold_list, start[0]);
+                    fold_list = add_cp_to_invlist(fold_list, folded);
+                    if (folds_to_this_cp_count > 0) {
+                        fold_list = add_cp_to_invlist(fold_list, first_fold);
+                        for (i = 0; i + 1 < folds_to_this_cp_count; i++) {
+                            fold_list = add_cp_to_invlist(fold_list,
+                                                        remaining_folds[i]);
                         }
-                        else {
-                            if (_invlist_contains_cp(PL_in_some_fold, value)) {
-                                op = EXACT;
+                    }
+
+                    /* If the fold list is identical to what's in this ANYOF
+                     * node, the node can be represented by an EXACTFish one
+                     * instead */
+                    if (_invlistEQ(*use_this_list, fold_list,
+                                   0 /* Don't complement */ )
+                    ) {
+
+                        /* But, we have to be careful, as mentioned above.
+                         * Just the right sequence of characters could match
+                         * this if it is part of a multi-character fold.  That
+                         * IS what we want if we are under /i.  But it ISN'T
+                         * what we want if not under /i, as it could match when
+                         * it shouldn't.  So, when we aren't under /i and this
+                         * character participates in a multi-char fold, we
+                         * don't optimize into an EXACTFish node.  So, for each
+                         * case below we have to check if we are folding
+                         * and if not, if it is not part of a multi-char fold.
+                         * */
+                        if (start[0] > 255) {    /* Highish code point */
+                            if (FOLD || ! _invlist_contains_cp(
+                                            PL_InMultiCharFold, folded))
+                            {
+                                op = (LOC)
+                                     ? EXACTFLU8
+                                     : (ASCII_FOLD_RESTRICTED)
+                                       ? EXACTFAA
+                                       : EXACTFU_ONLY8;
+                                value = folded;
                             }
+                        }   /* Below, the lowest code point < 256 */
+                        else if (    FOLD
+                                 &&  folded == 's'
+                                 &&  DEPENDS_SEMANTICS)
+                        {   /* An EXACTF node containing a single character
+                                's', can be an EXACTFU if it doesn't get
+                                joined with an adjacent 's' */
+                            op = EXACTFU_S_EDGE;
+                            value = folded;
                         }
+                        else if (    FOLD
+                                || ! HAS_NONLATIN1_FOLD_CLOSURE(start[0]))
+                        {
+                            if (upper_latin1_only_utf8_matches) {
+                                op = EXACTF;
 
-                        /* If we haven't found the node type, above, it means
-                         * we can use the prevailing one */
-                        if (op == END) {
-                            op = compute_EXACTish(pRExC_state);
+                                /* We can't use the fold, as that only matches
+                                 * under UTF-8 */
+                                value = start[0];
+                            }
+                            else if (     UNLIKELY(start[0] == MICRO_SIGN)
+                                     && ! UTF)
+                            {   /* EXACTFUP is a special node for this
+                                   character */
+                                op = (ASCII_FOLD_RESTRICTED)
+                                     ? EXACTFAA
+                                     : EXACTFUP;
+                                value = MICRO_SIGN;
+                            }
+                            else if (     ASCII_FOLD_RESTRICTED
+                                     && ! isASCII(start[0]))
+                            {   /* For ASCII under /iaa, we can use EXACTFU
+                                   below */
+                                op = EXACTFAA;
+                                value = folded;
+                            }
+                            else {
+                                op = EXACTFU;
+                                value = folded;
+                            }
                         }
                     }
-                }
-            }   /* End of first range contains just a single code point */
-            else if (start == 0) {
-                if (end == UV_MAX) {
-                    op = SANY;
-                    MARK_NAUGHTY(1);
-                }
-                else if (end == '\n' - 1
-                        && invlist_iternext(cp_list, &start, &end)
-                        && start == '\n' + 1 && end == UV_MAX)
-                {
-                    op = REG_ANY;
-                    MARK_NAUGHTY(1);
+
+                    SvREFCNT_dec_NN(fold_list);
+                    SvREFCNT_dec(all_cp_list);
                 }
             }
-            invlist_iterfinish(cp_list);
 
             if (op != END) {
-                if (PL_regkind[op] != EXACT) {
-                    ret = reg_node(pRExC_state, op);
+
+                /* Here, we have calculated what EXACTish node we would use.
+                 * But we don't use it if it would require converting the
+                 * pattern to UTF-8, unless not using it could cause us to miss
+                 * some folds (hence be buggy) */
+
+                if (! UTF && value > 255) {
+                    SV * in_multis = NULL;
+
+                    assert(FOLD);
+
+                    /* If there is no code point that is part of a multi-char
+                     * fold, then there aren't any matches, so we don't do this
+                     * optimization.  Otherwise, it could match depending on
+                     * the context around us, so we do upgrade */
+                    _invlist_intersection(PL_InMultiCharFold, cp_list, &in_multis);
+                    if (UNLIKELY(_invlist_len(in_multis) != 0)) {
+                        REQUIRE_UTF8(flagp);
+                    }
+                    else {
+                        op = END;
+                    }
                 }
-                else {
+
+                if (op != END) {
                     U8 len = (UTF) ? UVCHR_SKIP(value) : 1;
 
                     ret = regnode_guts(pRExC_state, op, len, "exact");
@@ -18277,16 +18804,17 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                     RExC_emit += 1 + STR_SZ(len);
                     STR_LEN(REGNODE_p(ret)) = len;
                     if (len == 1) {
-                        *STRING(REGNODE_p(ret)) = value;
+                        *STRING(REGNODE_p(ret)) = (U8) value;
                     }
                     else {
                         uvchr_to_utf8((U8 *) STRING(REGNODE_p(ret)), value);
                     }
+                    goto not_anyof;
                 }
-                goto not_anyof;
             }
+        }
 
-            {
+        if (! has_runtime_dependency) {
 
             /* See if this can be turned into an ANYOFM node.  Think about the
              * bit patterns in two different bytes.  In some positions, the
@@ -18307,7 +18835,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
              * 0x30.  Any other bytes ANDed yield something else.  So [01],
              * which is a common usage, is optimizable into ANYOFM, and can
              * benefit from the speed up.  We can only do this on UTF-8
-             * invariant bytes, because they don't have the same patterns under
+             * invariant bytes, because they have the same bit patterns under
              * UTF-8 as not. */
             PERL_UINT_FAST8_T inverted = 0;
 #ifdef EBCDIC
@@ -18324,9 +18852,10 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
             }
 
             if (invlist_highest(cp_list) <= max_permissible) {
-                UV this_start, this_end, lowest_cp;
+                UV this_start, this_end;
+                UV lowest_cp = UV_MAX;  /* inited to suppress compiler warn */
                 U8 bits_differing = 0;
-                Size_t cp_count = 0;
+                Size_t full_cp_count = 0;
                 bool first_time = TRUE;
 
                 /* Go through the bytes and find the bit positions that differ
@@ -18359,9 +18888,8 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                         bits_differing  |= i ^ lowest_cp;
                     }
 
-                    cp_count += this_end - this_start + 1;
+                    full_cp_count += this_end - this_start + 1;
                 }
-                invlist_iterfinish(cp_list);
 
                 /* At the end of the loop, we count how many bits differ from
                  * the bits in lowest code point, call the count 'd'.  If the
@@ -18376,8 +18904,8 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                  * a 1 in that position, and another has a 0.  But that would
                  * mean that one of them differs from the lowest code point in
                  * that position, which possibility we've already excluded.  */
-                if (  (inverted || cp_count > 1)
-                    && cp_count == 1U << PL_bitcount[bits_differing])
+                if (  (inverted || full_cp_count > 1)
+                    && full_cp_count == 1U << PL_bitcount[bits_differing])
                 {
                     U8 ANYOFM_mask;
 
@@ -18389,10 +18917,11 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                     /* The argument is the lowest code point */
                     ret = reganode(pRExC_state, op, lowest_cp);
                     FLAGS(REGNODE_p(ret)) = ANYOFM_mask;
-
                 }
+
+              done_anyofm:
+                invlist_iterfinish(cp_list);
             }
-          done_anyofm:
 
             if (inverted) {
                 _invlist_invert(cp_list);
@@ -18401,62 +18930,209 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
             if (op != END) {
                 goto not_anyof;
             }
-            }
+        }
 
-            /* Here, didn't find an optimization.  See if this matches any
-             * of the POSIX classes.  The POSIXA ones are about the same speed
-             * as ANYOF ops, but take less room; the ones that have
-             * above-Latin1 code point matches are somewhat faster than ANYOF.
-             * */
+        if (! (anyof_flags & ANYOF_LOCALE_FLAGS)) {
+            PERL_UINT_FAST8_T type;
+            SV * intersection = NULL;
+            SV* d_invlist = NULL;
 
-            for (posix_class = 0;
-                 posix_class <= _HIGHEST_REGCOMP_DOT_H_SYNC;
-                 posix_class++)
-            {
-                int try_inverted;
+            /* See if this matches any of the POSIX classes.  The POSIXA and
+             * POSIXD ones are about the same speed as ANYOF ops, but take less
+             * room; the ones that have above-Latin1 code point matches are
+             * somewhat faster than ANYOF.  */
+
+            for (type = POSIXA; type >= POSIXD; type--) {
+                int posix_class;
+
+                if (type == POSIXL) {   /* But not /l posix classes */
+                    continue;
+                }
 
-                for (try_inverted = 0; try_inverted < 2; try_inverted++)
+                for (posix_class = 0;
+                     posix_class <= _HIGHEST_REGCOMP_DOT_H_SYNC;
+                     posix_class++)
                 {
+                    SV** our_code_points = &cp_list;
+                    SV** official_code_points;
+                    int try_inverted;
+
+                    if (type == POSIXA) {
+                        official_code_points = &PL_Posix_ptrs[posix_class];
+                    }
+                    else {
+                        official_code_points = &PL_XPosix_ptrs[posix_class];
+                    }
+
+                    /* Skip non-existent classes of this type.  e.g. \v only
+                     * has an entry in PL_XPosix_ptrs */
+                    if (! *official_code_points) {
+                        continue;
+                    }
+
+                    /* Try both the regular class, and its inversion */
+                    for (try_inverted = 0; try_inverted < 2; try_inverted++) {
+                        bool this_inverted = invert ^ try_inverted;
+
+                        if (type != POSIXD) {
+
+                            /* This class that isn't /d can't match if we have
+                             * /d dependencies */
+                            if (has_runtime_dependency
+                                                    & HAS_D_RUNTIME_DEPENDENCY)
+                            {
+                                continue;
+                            }
+                        }
+                        else /* is /d */ if (! this_inverted) {
+
+                            /* /d classes don't match anything non-ASCII below
+                             * 256 unconditionally (which cp_list contains) */
+                            _invlist_intersection(cp_list, PL_UpperLatin1,
+                                                           &intersection);
+                            if (_invlist_len(intersection) != 0) {
+                                continue;
+                            }
+
+                            SvREFCNT_dec(d_invlist);
+                            d_invlist = invlist_clone(cp_list, NULL);
+
+                            /* But under UTF-8 it turns into using /u rules.
+                             * Add the things it matches under these conditions
+                             * so that we check below that these are identical
+                             * to what the tested class should match */
+                            if (upper_latin1_only_utf8_matches) {
+                                _invlist_union(
+                                            d_invlist,
+                                            upper_latin1_only_utf8_matches,
+                                            &d_invlist);
+                            }
+                            our_code_points = &d_invlist;
+                        }
+                        else {  /* POSIXD, inverted.  If this doesn't have this
+                                   flag set, it isn't /d. */
+                            if (! (anyof_flags & ANYOF_SHARED_d_MATCHES_ALL_NON_UTF8_NON_ASCII_non_d_WARN_SUPER))
+                            {
+                                continue;
+                            }
+                            our_code_points = &cp_list;
+                        }
 
-                    /* Check if matches POSIXA, normal or inverted */
-                    if (PL_Posix_ptrs[posix_class]) {
-                        if (_invlistEQ(cp_list,
-                                       PL_Posix_ptrs[posix_class],
+                        /* Here, have weeded out some things.  We want to see
+                         * if the list of characters this node contains
+                         * ('*our_code_points') precisely matches those of the
+                         * class we are currently checking against
+                         * ('*official_code_points'). */
+                        if (_invlistEQ(*our_code_points,
+                                       *official_code_points,
                                        try_inverted))
                         {
+                            /* Here, they precisely match.  Optimize this ANYOF
+                             * node into its equivalent POSIX one of the
+                             * correct type, possibly inverted */
                             ret = reg_node(pRExC_state, (try_inverted)
-                                                        ? NPOSIXA
-                                                        : POSIXA);
-                        FLAGS(REGNODE_p(ret)) = posix_class;
+                                                        ? type + NPOSIXA
+                                                                - POSIXA
+                                                        : type);
+                            FLAGS(REGNODE_p(ret)) = posix_class;
+                            SvREFCNT_dec(d_invlist);
+                            SvREFCNT_dec(intersection);
                             goto not_anyof;
                         }
                     }
+                }
+            }
+            SvREFCNT_dec(d_invlist);
+            SvREFCNT_dec(intersection);
+        }
 
-                    /* Check if matches POSIXU, normal or inverted */
-                    if (_invlistEQ(cp_list,
-                                   PL_XPosix_ptrs[posix_class],
-                                   try_inverted))
-                    {
-                        ret = reg_node(pRExC_state, (try_inverted)
-                                                    ? NPOSIXU
-                                                    : POSIXU);
+        /* If didn't find an optimization and there is no need for a bitmap,
+         * optimize to indicate that */
+        if (     start[0] >= NUM_ANYOF_CODE_POINTS
+            && ! LOC
+            && ! upper_latin1_only_utf8_matches
+            &&   anyof_flags == 0)
+        {
+            U8 low_utf8[UTF8_MAXBYTES+1];
+            UV highest_cp = invlist_highest(cp_list);
+
+            op = ANYOFH;
+
+            /* Currently the maximum allowed code point by the system is
+             * IV_MAX.  Higher ones are reserved for future internal use.  This
+             * particular regnode can be used for higher ones, but we can't
+             * calculate the code point of those.  IV_MAX suffices though, as
+             * it will be a large first byte */
+            (void) uvchr_to_utf8(low_utf8, MIN(start[0], IV_MAX));
+
+            /* We store the lowest possible first byte of the UTF-8
+             * representation, using the flags field.  This allows for quick
+             * ruling out of some inputs without having to convert from UTF-8
+             * to code point.  For EBCDIC, this has to be I8. */
+            anyof_flags = NATIVE_UTF8_TO_I8(low_utf8[0]);
+
+            /* If the first UTF-8 start byte for the highest code point in the
+             * range is suitably small, we may be able to get an upper bound as
+             * well */
+            if (highest_cp <= IV_MAX) {
+                U8 high_utf8[UTF8_MAXBYTES+1];
+
+                (void) uvchr_to_utf8(high_utf8, highest_cp);
+
+                /* If the lowest and highest are the same, we can get an exact
+                 * first byte instead of a just minimum.  We signal this with a
+                 * different regnode */
+                if (low_utf8[0] == high_utf8[0]) {
+
+                    /* No need to convert to I8 for EBCDIC as this is an exact
+                     * match */
+                    anyof_flags = low_utf8[0];
+                    op = ANYOFHb;
+                }
+                else if (NATIVE_UTF8_TO_I8(high_utf8[0]) <= MAX_ANYOF_HRx_BYTE)
+                {
 
-                        FLAGS(REGNODE_p(ret)) = posix_class;
-                        goto not_anyof;
+                    /* Here, the high byte is not the same as the low, but is
+                     * small enough that its reasonable to have a loose upper
+                     * bound, which is packed in with the strict lower bound.
+                     * See comments at the definition of MAX_ANYOF_HRx_BYTE.
+                     * On EBCDIC platforms, I8 is used.  On ASCII platforms I8
+                     * is the same thing as UTF-8 */
+
+                    U8 bits = 0;
+                    U8 max_range_diff = MAX_ANYOF_HRx_BYTE - anyof_flags;
+                    U8 range_diff = NATIVE_UTF8_TO_I8(high_utf8[0])
+                                  - anyof_flags;
+
+                    if (range_diff <= max_range_diff / 8) {
+                        bits = 3;
+                    }
+                    else if (range_diff <= max_range_diff / 4) {
+                        bits = 2;
+                    }
+                    else if (range_diff <= max_range_diff / 2) {
+                        bits = 1;
                     }
+                    anyof_flags = (anyof_flags - 0xC0) << 2 | bits;
+                    op = ANYOFHr;
                 }
             }
+
+            goto done_finding_op;
         }
     }   /* End of seeing if can optimize it into a different node */
 
-    /* It's going to be an ANYOF node. */
-    op = (use_anyofd)
+  is_anyof: /* It's going to be an ANYOF node. */
+    op = (has_runtime_dependency & HAS_D_RUNTIME_DEPENDENCY)
          ? ANYOFD
          : ((posixl)
             ? ANYOFPOSIXL
             : ((LOC)
                ? ANYOFL
                : ANYOF));
+
+  done_finding_op:
+
     ret = regnode_guts(pRExC_state, op, regarglen[op], "anyof");
     FILL_NODE(ret, op);        /* We set the argument later */
     RExC_emit += 1 + regarglen[op];
@@ -18495,27 +19171,10 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
         ANYOF_FLAGS(REGNODE_p(ret)) |= ANYOF_SHARED_d_UPPER_LATIN1_UTF8_STRING_MATCHES_non_d_RUNTIME_USER_PROP;
     }
 
-    /* If there is a swash and more than one element, we can't use the swash in
-     * the optimization below. */
-    if (swash && element_count > 1) {
-       SvREFCNT_dec_NN(swash);
-       swash = NULL;
-    }
-
-    /* Note that the optimization of using 'swash' if it is the only thing in
-     * the class doesn't have us change swash at all, so it can include things
-     * that are also in the bitmap; otherwise we have purposely deleted that
-     * duplicate information */
     set_ANYOF_arg(pRExC_state, REGNODE_p(ret), cp_list,
                   (HAS_NONLOCALE_RUNTIME_PROPERTY_DEFINITION)
                    ? listsv : NULL,
-                  only_utf8_locale_list,
-                  swash, has_user_defined_property);
-
-    if (ANYOF_FLAGS(REGNODE_p(ret)) & ANYOF_LOCALE_FLAGS) {
-        RExC_contains_locale = 1;
-    }
-
+                  only_utf8_locale_list);
     return ret;
 
   not_anyof:
@@ -18525,7 +19184,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
 
     Set_Node_Offset_Length(REGNODE_p(ret), orig_parse - RExC_start,
                                            RExC_parse - orig_parse);;
-    SvREFCNT_dec_NN(cp_list);;
+    SvREFCNT_dec(cp_list);;
     return ret;
 }
 
@@ -18536,31 +19195,21 @@ S_set_ANYOF_arg(pTHX_ RExC_state_t* const pRExC_state,
                 regnode* const node,
                 SV* const cp_list,
                 SV* const runtime_defns,
-                SV* const only_utf8_locale_list,
-                SV* const swash,
-                const bool has_user_defined_property)
+                SV* const only_utf8_locale_list)
 {
     /* Sets the arg field of an ANYOF-type node 'node', using information about
      * the node passed-in.  If there is nothing outside the node's bitmap, the
      * arg is set to ANYOF_ONLY_HAS_BITMAP.  Otherwise, it sets the argument to
      * the count returned by add_data(), having allocated and stored an array,
-     * av, that that count references, as follows:
-     *  av[0] stores the character class description in its textual form.
-     *        This is used later (regexec.c:Perl_regclass_swash()) to
-     *        initialize the appropriate swash, and is also useful for dumping
-     *        the regnode.  This is set to &PL_sv_undef if the textual
-     *        description is not needed at run-time (as happens if the other
-     *        elements completely define the class)
-     *  av[1] if &PL_sv_undef, is a placeholder to later contain the swash
-     *        computed from av[0].  But if no further computation need be done,
-     *        the swash is stored here now (and av[0] is &PL_sv_undef).
-     *  av[2] stores the inversion list of code points that match only if the
-     *        current locale is UTF-8
-     *  av[3] stores the cp_list inversion list for use in addition or instead
-     *        of av[0]; used only if cp_list exists and av[1] is &PL_sv_undef.
-     *        (Otherwise everything needed is already in av[0] and av[1])
-     *  av[4] is set if any component of the class is from a user-defined
-     *        property; used only if av[3] exists */
+     * av, as follows:
+     *
+     *  av[0] stores the inversion list defining this class as far as known at
+     *        this time, or PL_sv_undef if nothing definite is now known.
+     *  av[1] stores the inversion list of code points that match only if the
+     *        current locale is UTF-8, or if none, PL_sv_undef if there is an
+     *        av[2], or no entry otherwise.
+     *  av[2] stores the list of user-defined properties whose subroutine
+     *        definitions aren't known at this time, or no entry if none. */
 
     UV n;
 
@@ -18575,26 +19224,16 @@ S_set_ANYOF_arg(pTHX_ RExC_state_t* const pRExC_state,
        AV * const av = newAV();
        SV *rv;
 
-       av_store(av, 0, (runtime_defns)
-                       ? SvREFCNT_inc(runtime_defns) : &PL_sv_undef);
-       if (swash) {
-           assert(cp_list);
-           av_store(av, 1, swash);
-           SvREFCNT_dec_NN(cp_list);
-       }
-       else {
-           av_store(av, 1, &PL_sv_undef);
-           if (cp_list) {
-               av_store(av, 3, cp_list);
-               av_store(av, 4, newSVuv(has_user_defined_property));
-           }
-       }
+        if (cp_list) {
+            av_store(av, INVLIST_INDEX, cp_list);
+        }
 
         if (only_utf8_locale_list) {
-           av_store(av, 2, only_utf8_locale_list);
+            av_store(av, ONLY_LOCALE_MATCHES_INDEX, only_utf8_locale_list);
         }
-        else {
-           av_store(av, 2, &PL_sv_undef);
+
+        if (runtime_defns) {
+            av_store(av, DEFERRED_USER_DEFINED_INDEX, SvREFCNT_inc(runtime_defns));
         }
 
        rv = newRV_noinc(MUTABLE_SV(av));
@@ -18615,14 +19254,15 @@ Perl__get_regclass_nonbitmap_data(pTHX_ const regexp *prog,
 
 {
     /* For internal core use only.
-     * Returns the swash for the input 'node' in the regex 'prog'.
-     * If <doinit> is 'true', will attempt to create the swash if not already
-     *   done.
+     * Returns the inversion list for the input 'node' in the regex 'prog'.
+     * If <doinit> is 'true', will attempt to create the inversion list if not
+     *    already done.
      * If <listsvp> is non-null, will return the printable contents of the
-     *    swash.  This can be used to get debugging information even before the
-     *    swash exists, by calling this function with 'doinit' set to false, in
-     *    which case the components that will be used to eventually create the
-     *    swash are returned  (in a printable form).
+     *    property definition.  This can be used to get debugging information
+     *    even before the inversion list exists, by calling this function with
+     *    'doinit' set to false, in which case the components that will be used
+     *    to eventually create the inversion list are returned  (in a printable
+     *    form).
      * If <only_utf8_locale_ptr> is not NULL, it is where this routine is to
      *    store an inversion list of code points that should match only if the
      *    execution-time locale is a UTF-8 one.
@@ -18630,18 +19270,17 @@ Perl__get_regclass_nonbitmap_data(pTHX_ const regexp *prog,
      *    inversion list of the code points that would be instead returned in
      *    <listsvp> if this were NULL.  Thus, what gets output in <listsvp>
      *    when this parameter is used, is just the non-code point data that
-     *    will go into creating the swash.  This currently should be just
+     *    will go into creating the inversion list.  This currently should be just
      *    user-defined properties whose definitions were not known at compile
      *    time.  Using this parameter allows for easier manipulation of the
-     *    swash's data by the caller.  It is illegal to call this function with
-     *    this parameter set, but not <listsvp>
+     *    inversion list's data by the caller.  It is illegal to call this
+     *    function with this parameter set, but not <listsvp>
      *
      * Tied intimately to how S_set_ANYOF_arg sets up the data structure.  Note
-     * that, in spite of this function's name, the swash it returns may include
-     * the bitmap data as well */
+     * that, in spite of this function's name, the inversion list it returns
+     * may include the bitmap data as well */
 
-    SV *sw  = NULL;
-    SV *si  = NULL;         /* Input swash initialization string */
+    SV *si  = NULL;         /* Input initialization string */
     SV* invlist = NULL;
 
     RXi_GET_DECL(prog, progi);
@@ -18657,69 +19296,73 @@ Perl__get_regclass_nonbitmap_data(pTHX_ const regexp *prog,
            SV * const rv = MUTABLE_SV(data->data[n]);
            AV * const av = MUTABLE_AV(SvRV(rv));
            SV **const ary = AvARRAY(av);
-           U8 swash_init_flags = _CORE_SWASH_INIT_ACCEPT_INVLIST;
 
-           si = *ary;  /* ary[0] = the string to initialize the swash with */
+            invlist = ary[INVLIST_INDEX];
 
-            if (av_tindex_skip_len_mg(av) >= 2) {
-                if (only_utf8_locale_ptr
-                    && ary[2]
-                    && ary[2] != &PL_sv_undef)
-                {
-                    *only_utf8_locale_ptr = ary[2];
-                }
-                else {
-                    assert(only_utf8_locale_ptr);
-                    *only_utf8_locale_ptr = NULL;
-                }
-
-                /* Elements 3 and 4 are either both present or both absent. [3]
-                 * is any inversion list generated at compile time; [4]
-                 * indicates if that inversion list has any user-defined
-                 * properties in it. */
-                if (av_tindex_skip_len_mg(av) >= 3) {
-                    invlist = ary[3];
-                    if (SvUV(ary[4])) {
-                        swash_init_flags |= _CORE_SWASH_INIT_USER_DEFINED_PROPERTY;
+            if (av_tindex_skip_len_mg(av) >= ONLY_LOCALE_MATCHES_INDEX) {
+                *only_utf8_locale_ptr = ary[ONLY_LOCALE_MATCHES_INDEX];
+            }
+
+            if (av_tindex_skip_len_mg(av) >= DEFERRED_USER_DEFINED_INDEX) {
+                si = ary[DEFERRED_USER_DEFINED_INDEX];
+            }
+
+           if (doinit && (si || invlist)) {
+                if (si) {
+                    bool user_defined;
+                    SV * msg = newSVpvs_flags("", SVs_TEMP);
+
+                    SV * prop_definition = handle_user_defined_property(
+                            "", 0, FALSE,   /* There is no \p{}, \P{} */
+                            SvPVX_const(si)[1] - '0',   /* /i or not has been
+                                                           stored here for just
+                                                           this occasion */
+                            TRUE,           /* run time */
+                            FALSE,          /* This call must find the defn */
+                            si,             /* The property definition  */
+                            &user_defined,
+                            msg,
+                            0               /* base level call */
+                           );
+
+                    if (SvCUR(msg)) {
+                        assert(prop_definition == NULL);
+
+                        Perl_croak(aTHX_ "%" UTF8f,
+                                UTF8fARG(SvUTF8(msg), SvCUR(msg), SvPVX(msg)));
                     }
-                }
-                else {
-                    invlist = NULL;
-                }
-           }
 
-           /* Element [1] is reserved for the set-up swash.  If already there,
-            * return it; if not, create it and store it there */
-           if (ary[1] && SvROK(ary[1])) {
-               sw = ary[1];
-           }
-           else if (doinit && ((si && si != &PL_sv_undef)
-                                 || (invlist && invlist != &PL_sv_undef))) {
-               assert(si);
-               sw = _core_swash_init("utf8", /* the utf8 package */
-                                     "", /* nameless */
-                                     si,
-                                     1, /* binary */
-                                     0, /* not from tr/// */
-                                     invlist,
-                                     &swash_init_flags);
-               (void)av_store(av, 1, sw);
+                    if (invlist) {
+                        _invlist_union(invlist, prop_definition, &invlist);
+                        SvREFCNT_dec_NN(prop_definition);
+                    }
+                    else {
+                        invlist = prop_definition;
+                    }
+
+                    STATIC_ASSERT_STMT(ONLY_LOCALE_MATCHES_INDEX == 1 + INVLIST_INDEX);
+                    STATIC_ASSERT_STMT(DEFERRED_USER_DEFINED_INDEX == 1 + ONLY_LOCALE_MATCHES_INDEX);
+
+                    av_store(av, INVLIST_INDEX, invlist);
+                    av_fill(av, (ary[ONLY_LOCALE_MATCHES_INDEX])
+                                 ? ONLY_LOCALE_MATCHES_INDEX:
+                                 INVLIST_INDEX);
+                    si = NULL;
+                }
            }
        }
     }
 
-    /* If requested, return a printable version of what this swash matches */
+    /* If requested, return a printable version of what this ANYOF node matches
+     * */
     if (listsvp) {
        SV* matches_string = NULL;
 
-        /* The swash should be used, if possible, to get the data, as it
-         * contains the resolved data.  But this function can be called at
-         * compile-time, before everything gets resolved, in which case we
-         * return the currently best available information, which is the string
-         * that will eventually be used to do that resolving, 'si' */
-       if ((! sw || (invlist = _get_swash_invlist(sw)) == NULL)
-            && (si && si != &PL_sv_undef))
-        {
+        /* This function can be called at compile-time, before everything gets
+         * resolved, in which case we return the currently best available
+         * information, which is the string that will eventually be used to do
+         * that resolving, 'si' */
+       if (si) {
             /* Here, we only have 'si' (and possibly some passed-in data in
              * 'invlist', which is handled below)  If the caller only wants
              * 'si', use that.  */
@@ -18812,12 +19455,10 @@ Perl__get_regclass_nonbitmap_data(pTHX_ const regexp *prog,
                 if (SvCUR(matches_string)) {  /* Get rid of trailing blank */
                     SvCUR_set(matches_string, SvCUR(matches_string) - 1);
                 }
-            } /* end of has an 'si' but no swash */
+            } /* end of has an 'si' */
        }
 
-        /* If we have a swash in place, its equivalent inversion list was above
-         * placed into 'invlist'.  If not, this variable may contain a stored
-         * inversion list which is information beyond what is in 'si' */
+        /* Add the stuff that's already known */
         if (invlist) {
 
             /* Again, if the caller doesn't want the output inversion list, put
@@ -18841,7 +19482,7 @@ Perl__get_regclass_nonbitmap_data(pTHX_ const regexp *prog,
        *listsvp = matches_string;
     }
 
-    return sw;
+    return invlist;
 }
 #endif /* !defined(PERL_IN_XSUB_RE) || defined(PLUGGABLE_RE_EXTENSION) */
 
@@ -18954,7 +19595,9 @@ S_nextchar(pTHX_ RExC_state_t *pRExC_state)
                || UTF8_IS_INVARIANT(*RExC_parse)
                || UTF8_IS_START(*RExC_parse));
 
-        RExC_parse += (UTF) ? UTF8SKIP(RExC_parse) : 1;
+        RExC_parse += (UTF)
+                      ? UTF8_SAFE_SKIP(RExC_parse, RExC_end)
+                      : 1;
 
         skip_to_be_ignored_text(pRExC_state, &RExC_parse,
                                 FALSE /* Don't force /x */ );
@@ -18964,6 +19607,9 @@ S_nextchar(pTHX_ RExC_state_t *pRExC_state)
 STATIC void
 S_change_engine_size(pTHX_ RExC_state_t *pRExC_state, const Ptrdiff_t size)
 {
+    /* 'size' is the delta to add or subtract from the current memory allocated
+     * to the regex engine being constructed */
+
     PERL_ARGS_ASSERT_CHANGE_ENGINE_SIZE;
 
     RExC_size += size;
@@ -19121,7 +19767,11 @@ S_reginsert(pTHX_ RExC_state_t *pRExC_state, const U8 op,
     src = REGNODE_p(RExC_emit);
     RExC_emit += size;
     dst = REGNODE_p(RExC_emit);
-    if (RExC_open_parens) {
+
+    /* If we are in a "count the parentheses" pass, the numbers are unreliable,
+     * and [perl #133871] shows this can lead to problems, so skip this
+     * realignment of parens until a later pass when they are reliable */
+    if (! IN_PARENS_PASS && RExC_open_parens) {
         int paren;
         /*DEBUG_PARSE_FMT("inst"," - %" IVdf, (IV)RExC_npar);*/
         /* remember that RExC_npar is rex->nparens + 1,
@@ -19194,10 +19844,13 @@ S_reginsert(pTHX_ RExC_state_t *pRExC_state, const U8 op,
 }
 
 /*
-- regtail - set the next-pointer at the end of a node chain of p to val.
+- regtail - set the next-pointer at the end of a node chain of p to val.  If
+            that value won't fit in the space available, instead returns FALSE.
+            (Except asserts if we can't fit in the largest space the regex
+            engine is designed for.)
 - SEE ALSO: regtail_study
 */
-STATIC void
+STATIC bool
 S_regtail(pTHX_ RExC_state_t * pRExC_state,
                 const regnode_offset p,
                 const regnode_offset val,
@@ -19219,7 +19872,7 @@ S_regtail(pTHX_ RExC_state_t * pRExC_state,
             DEBUG_PARSE_MSG((scan==p ? "tail" : ""));
             regprop(RExC_rx, RExC_mysv, REGNODE_p(scan), NULL, pRExC_state);
             Perl_re_printf( aTHX_  "~ %s (%d) %s %s\n",
-                SvPV_nolen_const(RExC_mysv), REG_NODE_NUM(REGNODE_p(scan)),
+                SvPV_nolen_const(RExC_mysv), scan,
                     (temp == NULL ? "->" : ""),
                     (temp == NULL ? PL_reg_name[OP(REGNODE_p(val))] : "")
             );
@@ -19230,11 +19883,21 @@ S_regtail(pTHX_ RExC_state_t * pRExC_state,
     }
 
     if (reg_off_by_arg[OP(REGNODE_p(scan))]) {
+        assert((UV) (val - scan) <= U32_MAX);
         ARG_SET(REGNODE_p(scan), val - scan);
     }
     else {
+        if (val - scan > U16_MAX) {
+            /* Since not all callers check the return value, populate this with
+             * something that won't loop and will likely lead to a crash if
+             * execution continues */
+            NEXT_OFF(REGNODE_p(scan)) = U16_MAX;
+            return FALSE;
+        }
         NEXT_OFF(REGNODE_p(scan)) = val - scan;
     }
+
+    return TRUE;
 }
 
 #ifdef DEBUGGING
@@ -19251,10 +19914,14 @@ that it is purely analytical.
 Currently only used when in DEBUG mode. The macro REGTAIL_STUDY() is used
 to control which is which.
 
+This used to return a value that was ignored.  It was a problem that it is
+#ifdef'd to be another function that didn't return a value.  khw has changed it
+so both currently return a pass/fail return.
+
 */
 /* TODO: All four parms should be const */
 
-STATIC U8
+STATIC bool
 S_regtail_study(pTHX_ RExC_state_t *pRExC_state, regnode_offset p,
                       const regnode_offset val, U32 depth)
 {
@@ -19278,7 +19945,7 @@ S_regtail_study(pTHX_ RExC_state_t *pRExC_state, regnode_offset p,
            bool unfolded_multi_char;   /* Unexamined in this routine */
             if (join_exact(pRExC_state, scan, &min,
                            &unfolded_multi_char, 1, REGNODE_p(val), depth+1))
-                return EXACT;
+                return TRUE; /* Was return EXACT */
        }
 #endif
         if ( exact ) {
@@ -19310,7 +19977,7 @@ S_regtail_study(pTHX_ RExC_state_t *pRExC_state, regnode_offset p,
             regprop(RExC_rx, RExC_mysv, REGNODE_p(scan), NULL, pRExC_state);
             Perl_re_printf( aTHX_  "~ %s (%d) -> %s\n",
                 SvPV_nolen_const(RExC_mysv),
-                REG_NODE_NUM(REGNODE_p(scan)),
+                scan,
                 PL_reg_name[exact]);
         });
        if (temp == NULL)
@@ -19323,18 +19990,23 @@ S_regtail_study(pTHX_ RExC_state_t *pRExC_state, regnode_offset p,
         Perl_re_printf( aTHX_
                       "~ attach to %s (%" IVdf ") offset to %" IVdf "\n",
                      SvPV_nolen_const(RExC_mysv),
-                     (IV)REG_NODE_NUM(REGNODE_p(val)),
+                     (IV)val,
                      (IV)(val - scan)
         );
     });
     if (reg_off_by_arg[OP(REGNODE_p(scan))]) {
+        assert((UV) (val - scan) <= U32_MAX);
        ARG_SET(REGNODE_p(scan), val - scan);
     }
     else {
+        if (val - scan > U16_MAX) {
+            NEXT_OFF(REGNODE_p(scan)) = U16_MAX;
+            return FALSE;
+        }
        NEXT_OFF(REGNODE_p(scan)) = val - scan;
     }
 
-    return exact;
+    return TRUE; /* Was 'return exact' */
 }
 #endif
 
@@ -19596,6 +20268,7 @@ void
 Perl_regprop(pTHX_ const regexp *prog, SV *sv, const regnode *o, const regmatch_info *reginfo, const RExC_state_t *pRExC_state)
 {
 #ifdef DEBUGGING
+    dVAR;
     int k;
     RXi_GET_DECL(prog, progi);
     GET_RE_DEBUG_FLAGS_DECL;
@@ -19691,7 +20364,7 @@ Perl_regprop(pTHX_ const regexp *prog, SV *sv, const regnode *o, const regmatch_
             name_list= RExC_paren_name_list;
         }
         if (name_list) {
-            if ( k != REF || (OP(o) < NREF)) {
+            if ( k != REF || (OP(o) < REFN)) {
                 SV **name= av_fetch(name_list, parno, 0 );
                if (name)
                    Perl_sv_catpvf(aTHX_ sv, " '%" SVf "'", SVfARG(*name));
@@ -19745,7 +20418,9 @@ Perl_regprop(pTHX_ const regexp *prog, SV *sv, const regnode *o, const regmatch_
         /* 2: embedded, otherwise 1 */
        Perl_sv_catpvf(aTHX_ sv, "[%d]", o->flags);
     else if (k == ANYOF) {
-       const U8 flags = ANYOF_FLAGS(o);
+       const U8 flags = inRANGE(OP(o), ANYOFH, ANYOFHr)
+                          ? 0
+                          : ANYOF_FLAGS(o);
         bool do_sep = FALSE;    /* Do we need to separate various components of
                                    the output? */
         /* Set if there is still an unresolved user-defined property */
@@ -19801,42 +20476,46 @@ Perl_regprop(pTHX_ const regexp *prog, SV *sv, const regnode *o, const regmatch_
         /* Ready to start outputting.  First, the initial left bracket */
        Perl_sv_catpvf(aTHX_ sv, "[%s", PL_colors[0]);
 
-        /* Then all the things that could fit in the bitmap */
-        do_sep = put_charclass_bitmap_innards(sv,
-                                              ANYOF_BITMAP(o),
-                                              bitmap_range_not_in_bitmap,
-                                              only_utf8_locale_invlist,
-                                              o,
-
-                                              /* Can't try inverting for a
-                                               * better display if there are
-                                               * things that haven't been
-                                               * resolved */
-                                              unresolved != NULL);
-        SvREFCNT_dec(bitmap_range_not_in_bitmap);
-
-        /* If there are user-defined properties which haven't been defined yet,
-         * output them.  If the result is not to be inverted, it is clearest to
-         * output them in a separate [] from the bitmap range stuff.  If the
-         * result is to be complemented, we have to show everything in one [],
-         * as the inversion applies to the whole thing.  Use {braces} to
-         * separate them from anything in the bitmap and anything above the
-         * bitmap. */
-        if (unresolved) {
-            if (inverted) {
-                if (! do_sep) { /* If didn't output anything in the bitmap */
-                    sv_catpvs(sv, "^");
+        if (! inRANGE(OP(o), ANYOFH, ANYOFHr)) {
+            /* Then all the things that could fit in the bitmap */
+            do_sep = put_charclass_bitmap_innards(sv,
+                                                  ANYOF_BITMAP(o),
+                                                  bitmap_range_not_in_bitmap,
+                                                  only_utf8_locale_invlist,
+                                                  o,
+
+                                                  /* Can't try inverting for a
+                                                   * better display if there
+                                                   * are things that haven't
+                                                   * been resolved */
+                                                  unresolved != NULL);
+            SvREFCNT_dec(bitmap_range_not_in_bitmap);
+
+            /* If there are user-defined properties which haven't been defined
+             * yet, output them.  If the result is not to be inverted, it is
+             * clearest to output them in a separate [] from the bitmap range
+             * stuff.  If the result is to be complemented, we have to show
+             * everything in one [], as the inversion applies to the whole
+             * thing.  Use {braces} to separate them from anything in the
+             * bitmap and anything above the bitmap. */
+            if (unresolved) {
+                if (inverted) {
+                    if (! do_sep) { /* If didn't output anything in the bitmap
+                                     */
+                        sv_catpvs(sv, "^");
+                    }
+                    sv_catpvs(sv, "{");
                 }
-                sv_catpvs(sv, "{");
-            }
-            else if (do_sep) {
-                Perl_sv_catpvf(aTHX_ sv,"%s][%s", PL_colors[1], PL_colors[0]);
-            }
-            sv_catsv(sv, unresolved);
-            if (inverted) {
-                sv_catpvs(sv, "}");
+                else if (do_sep) {
+                    Perl_sv_catpvf(aTHX_ sv,"%s][%s", PL_colors[1],
+                                                      PL_colors[0]);
+                }
+                sv_catsv(sv, unresolved);
+                if (inverted) {
+                    sv_catpvs(sv, "}");
+                }
+                do_sep = ! inverted;
             }
-            do_sep = ! inverted;
         }
 
         /* And, finally, add the above-the-bitmap stuff */
@@ -19895,6 +20574,22 @@ Perl_regprop(pTHX_ const regexp *prog, SV *sv, const regnode *o, const regmatch_
         /* And finally the matching, closing ']' */
        Perl_sv_catpvf(aTHX_ sv, "%s]", PL_colors[1]);
 
+        if (inRANGE(OP(o), ANYOFH, ANYOFHr)) {
+            U8 lowest = (OP(o) != ANYOFHr)
+                         ? FLAGS(o)
+                         : LOWEST_ANYOF_HRx_BYTE(FLAGS(o));
+            U8 highest = (OP(o) == ANYOFHb)
+                         ? lowest
+                         : OP(o) == ANYOFH
+                           ? 0xFF
+                           : HIGHEST_ANYOF_HRx_BYTE(FLAGS(o));
+            Perl_sv_catpvf(aTHX_ sv, " (First UTF-8 byte=%02X", lowest);
+            if (lowest != highest) {
+                Perl_sv_catpvf(aTHX_ sv, "-%02X", highest);
+            }
+            Perl_sv_catpvf(aTHX_ sv, ")");
+        }
+
         SvREFCNT_dec(unresolved);
     }
     else if (k == ANYOFM) {
@@ -19937,8 +20632,13 @@ Perl_regprop(pTHX_ const regexp *prog, SV *sv, const regnode *o, const regmatch_
         assert(FLAGS(o) < C_ARRAY_LENGTH(bounds));
         sv_catpv(sv, bounds[FLAGS(o)]);
     }
-    else if (k == BRANCHJ && (OP(o) == UNLESSM || OP(o) == IFMATCH))
-       Perl_sv_catpvf(aTHX_ sv, "[%d]", -(o->flags));
+    else if (k == BRANCHJ && (OP(o) == UNLESSM || OP(o) == IFMATCH)) {
+       Perl_sv_catpvf(aTHX_ sv, "[%d", -(o->flags));
+        if (o->next_off) {
+            Perl_sv_catpvf(aTHX_ sv, "..-%d", o->flags - o->next_off);
+        }
+       Perl_sv_catpvf(aTHX_ sv, "]");
+    }
     else if (OP(o) == SBOL)
         Perl_sv_catpvf(aTHX_ sv, " /%s/", o->flags ? "\\A" : "^");
 
@@ -20082,7 +20782,23 @@ Perl_reg_temp_copy(pTHX_ REGEXP *dsv, REGEXP *ssv)
     if (!dsv)
        dsv = (REGEXP*) newSV_type(SVt_REGEXP);
     else {
+        assert(SvTYPE(dsv) == SVt_REGEXP || (SvTYPE(dsv) == SVt_PVLV));
+
+        /* our only valid caller, sv_setsv_flags(), should have done
+         * a SV_CHECK_THINKFIRST_COW_DROP() by now */
+        assert(!SvOOK(dsv));
+        assert(!SvIsCOW(dsv));
+        assert(!SvROK(dsv));
+
+        if (SvPVX_const(dsv)) {
+            if (SvLEN(dsv))
+                Safefree(SvPVX(dsv));
+            SvPVX(dsv) = NULL;
+        }
+        SvLEN_set(dsv, 0);
+        SvCUR_set(dsv, 0);
        SvOK_off((SV *)dsv);
+
        if (islv) {
            /* For PVLVs, the head (sv_any) points to an XPVLV, while
              * the LV's xpvlenu_rx will point to a regexp body, which
@@ -20373,6 +21089,11 @@ Perl_re_dup_guts(pTHX_ const REGEXP *sstr, REGEXP *dstr, CLONE_PARAMS *param)
               2: something we no longer hold a reference on
               so we need to copy it locally.  */
     RX_WRAPPED(dstr) = SAVEPVN(RX_WRAPPED_const(sstr), SvCUR(sstr)+1);
+    /* set malloced length to a non-zero value so it will be freed
+     * (otherwise in combination with SVf_FAKE it looks like an alien
+     * buffer). It doesn't have to be the actual malloced size, since it
+     * should never be grown */
+    SvLEN_set(dstr, SvCUR(sstr)+1);
     ret->mother_re   = NULL;
 }
 #endif /* PERL_IN_XSUB_RE */
@@ -20884,6 +21605,7 @@ S_put_charclass_bitmap_innards_common(pTHX_
      * output would have been only the inversion indicator '^', NULL is instead
      * returned. */
 
+    dVAR;
     SV * output;
 
     PERL_ARGS_ASSERT_PUT_CHARCLASS_BITMAP_INNARDS_COMMON;
@@ -20987,6 +21709,8 @@ S_put_charclass_bitmap_innards(pTHX_ SV *sv,
      * whether the class itself is to be inverted.  However,  there are some
      * cases where it can't try inverting, as what actually matches isn't known
      * until runtime, and hence the inversion isn't either. */
+
+    dVAR;
     bool inverting_allowed = ! force_as_is_display;
 
     int i;
@@ -21381,6 +22105,17 @@ S_dumpuntil(pTHX_ const regexp *r, const regnode *start, const regnode *node,
 void
 Perl_init_uniprops(pTHX)
 {
+    dVAR;
+
+    PL_user_def_props = newHV();
+
+#ifdef USE_ITHREADS
+
+    HvSHAREKEYS_off(PL_user_def_props);
+    PL_user_def_props_aTHX = aTHX;
+
+#endif
+
     /* Set up the inversion list global variables */
 
     PL_XPosix_ptrs[_CC_ASCII] = _new_invlist_C_array(uni_prop_ptrs[UNI_ASCII]);
@@ -21438,8 +22173,10 @@ Perl_init_uniprops(pTHX)
     PL_in_some_fold = _new_invlist_C_array(uni_prop_ptrs[UNI__PERL_ANY_FOLDS]);
     PL_HasMultiCharFold = _new_invlist_C_array(uni_prop_ptrs[
                                             UNI__PERL_FOLDS_TO_MULTI_CHAR]);
-    PL_InMultiCharFold = _new_invlist_C_array(UNI__PERL_IS_IN_MULTI_CHAR_FOLD_invlist);
-    PL_NonFinalFold = _new_invlist_C_array(UNI__PERL_NON_FINAL_FOLDS_invlist);
+    PL_InMultiCharFold = _new_invlist_C_array(uni_prop_ptrs[
+                                            UNI__PERL_IS_IN_MULTI_CHAR_FOLD]);
+    PL_NonFinalFold = _new_invlist_C_array(uni_prop_ptrs[
+                                            UNI__PERL_NON_FINAL_FOLDS]);
 
     PL_utf8_toupper = _new_invlist_C_array(Uppercase_Mapping_invlist);
     PL_utf8_tolower = _new_invlist_C_array(Lowercase_Mapping_invlist);
@@ -21448,6 +22185,8 @@ Perl_init_uniprops(pTHX)
     PL_utf8_tosimplefold = _new_invlist_C_array(Simple_Case_Folding_invlist);
     PL_utf8_foldclosures = _new_invlist_C_array(_Perl_IVCF_invlist);
     PL_utf8_mark = _new_invlist_C_array(uni_prop_ptrs[UNI_M]);
+    PL_CCC_non0_non230 = _new_invlist_C_array(_Perl_CCC_non0_non230_invlist);
+    PL_Private_Use = _new_invlist_C_array(uni_prop_ptrs[UNI_CO]);
 
 #ifdef UNI_XIDC
     /* The below are used only by deprecated functions.  They could be removed */
@@ -21457,39 +22196,488 @@ Perl_init_uniprops(pTHX)
 #endif
 }
 
-SV *
-Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
-                                const bool to_fold, bool * invert)
-{
-    /* Parse the interior meat of \p{} passed to this in 'name' with length
-     * 'name_len', and return an inversion list if a property with 'name' is
-     * found, or NULL if not.  'name' point to the input with leading and
-     * trailing space trimmed.  'to_fold' indicates if /i is in effect.
-     *
-     * When the return is an inversion list, '*invert' will be set to a boolean
-     * indicating if it should be inverted or not
-     *
-     * This currently doesn't handle all cases.  A NULL return indicates the
-     * caller should try a different approach
-     */
+#if 0
 
-    char* lookup_name;
-    bool stricter = FALSE;
-    bool is_nv_type = FALSE;         /* nv= or numeric_value=, or possibly one
-                                        of the cjk numeric properties (though
-                                        it requires extra effort to compile
-                                        them) */
-    unsigned int i;
-    unsigned int j = 0, lookup_len;
-    int equals_pos = -1;        /* Where the '=' is found, or negative if none */
-    int slash_pos = -1;        /* Where the '/' is found, or negative if none */
-    int table_index = 0;
-    bool starts_with_In_or_Is = FALSE;
-    Size_t lookup_offset = 0;
+This code was mainly added for backcompat to give a warning for non-portable
+code points in user-defined properties.  But experiments showed that the
+warning in earlier perls were only omitted on overflow, which should be an
+error, so there really isnt a backcompat issue, and actually adding the
+warning when none was present before might cause breakage, for little gain.  So
+khw left this code in, but not enabled.  Tests were never added.
+
+embed.fnc entry:
+Ei     |const char *|get_extended_utf8_msg|const UV cp
+
+PERL_STATIC_INLINE const char *
+S_get_extended_utf8_msg(pTHX_ const UV cp)
+{
+    U8 dummy[UTF8_MAXBYTES + 1];
+    HV *msgs;
+    SV **msg;
+
+    uvchr_to_utf8_flags_msgs(dummy, cp, UNICODE_WARN_PERL_EXTENDED,
+                             &msgs);
+
+    msg = hv_fetchs(msgs, "text", 0);
+    assert(msg);
+
+    (void) sv_2mortal((SV *) msgs);
+
+    return SvPVX(*msg);
+}
+
+#endif
+
+SV *
+Perl_handle_user_defined_property(pTHX_
+
+    /* Parses the contents of a user-defined property definition; returning the
+     * expanded definition if possible.  If so, the return is an inversion
+     * list.
+     *
+     * If there are subroutines that are part of the expansion and which aren't
+     * known at the time of the call to this function, this returns what
+     * parse_uniprop_string() returned for the first one encountered.
+     *
+     * If an error was found, NULL is returned, and 'msg' gets a suitable
+     * message appended to it.  (Appending allows the back trace of how we got
+     * to the faulty definition to be displayed through nested calls of
+     * user-defined subs.)
+     *
+     * The caller IS responsible for freeing any returned SV.
+     *
+     * The syntax of the contents is pretty much described in perlunicode.pod,
+     * but we also allow comments on each line */
+
+    const char * name,          /* Name of property */
+    const STRLEN name_len,      /* The name's length in bytes */
+    const bool is_utf8,         /* ? Is 'name' encoded in UTF-8 */
+    const bool to_fold,         /* ? Is this under /i */
+    const bool runtime,         /* ? Are we in compile- or run-time */
+    const bool deferrable,      /* Is it ok for this property's full definition
+                                   to be deferred until later? */
+    SV* contents,               /* The property's definition */
+    bool *user_defined_ptr,     /* This will be set TRUE as we wouldn't be
+                                   getting called unless this is thought to be
+                                   a user-defined property */
+    SV * msg,                   /* Any error or warning msg(s) are appended to
+                                   this */
+    const STRLEN level)         /* Recursion level of this call */
+{
+    STRLEN len;
+    const char * string         = SvPV_const(contents, len);
+    const char * const e        = string + len;
+    const bool is_contents_utf8 = cBOOL(SvUTF8(contents));
+    const STRLEN msgs_length_on_entry = SvCUR(msg);
+
+    const char * s0 = string;   /* Points to first byte in the current line
+                                   being parsed in 'string' */
+    const char overflow_msg[] = "Code point too large in \"";
+    SV* running_definition = NULL;
+
+    PERL_ARGS_ASSERT_HANDLE_USER_DEFINED_PROPERTY;
+
+    *user_defined_ptr = TRUE;
+
+    /* Look at each line */
+    while (s0 < e) {
+        const char * s;     /* Current byte */
+        char op = '+';      /* Default operation is 'union' */
+        IV   min = 0;       /* range begin code point */
+        IV   max = -1;      /* and range end */
+        SV* this_definition;
+
+        /* Skip comment lines */
+        if (*s0 == '#') {
+            s0 = strchr(s0, '\n');
+            if (s0 == NULL) {
+                break;
+            }
+            s0++;
+            continue;
+        }
+
+        /* For backcompat, allow an empty first line */
+        if (*s0 == '\n') {
+            s0++;
+            continue;
+        }
+
+        /* First character in the line may optionally be the operation */
+        if (   *s0 == '+'
+            || *s0 == '!'
+            || *s0 == '-'
+            || *s0 == '&')
+        {
+            op = *s0++;
+        }
+
+        /* If the line is one or two hex digits separated by blank space, its
+         * a range; otherwise it is either another user-defined property or an
+         * error */
+
+        s = s0;
+
+        if (! isXDIGIT(*s)) {
+            goto check_if_property;
+        }
+
+        do { /* Each new hex digit will add 4 bits. */
+            if (min > ( (IV) MAX_LEGAL_CP >> 4)) {
+                s = strchr(s, '\n');
+                if (s == NULL) {
+                    s = e;
+                }
+                if (SvCUR(msg) > 0) sv_catpvs(msg, "; ");
+                sv_catpv(msg, overflow_msg);
+                Perl_sv_catpvf(aTHX_ msg, "%" UTF8f,
+                                     UTF8fARG(is_contents_utf8, s - s0, s0));
+                sv_catpvs(msg, "\"");
+                goto return_failure;
+            }
+
+            /* Accumulate this digit into the value */
+            min = (min << 4) + READ_XDIGIT(s);
+        } while (isXDIGIT(*s));
+
+        while (isBLANK(*s)) { s++; }
+
+        /* We allow comments at the end of the line */
+        if (*s == '#') {
+            s = strchr(s, '\n');
+            if (s == NULL) {
+                s = e;
+            }
+            s++;
+        }
+        else if (s < e && *s != '\n') {
+            if (! isXDIGIT(*s)) {
+                goto check_if_property;
+            }
+
+            /* Look for the high point of the range */
+            max = 0;
+            do {
+                if (max > ( (IV) MAX_LEGAL_CP >> 4)) {
+                    s = strchr(s, '\n');
+                    if (s == NULL) {
+                        s = e;
+                    }
+                    if (SvCUR(msg) > 0) sv_catpvs(msg, "; ");
+                    sv_catpv(msg, overflow_msg);
+                    Perl_sv_catpvf(aTHX_ msg, "%" UTF8f,
+                                      UTF8fARG(is_contents_utf8, s - s0, s0));
+                    sv_catpvs(msg, "\"");
+                    goto return_failure;
+                }
+
+                max = (max << 4) + READ_XDIGIT(s);
+            } while (isXDIGIT(*s));
+
+            while (isBLANK(*s)) { s++; }
+
+            if (*s == '#') {
+                s = strchr(s, '\n');
+                if (s == NULL) {
+                    s = e;
+                }
+            }
+            else if (s < e && *s != '\n') {
+                goto check_if_property;
+            }
+        }
+
+        if (max == -1) {    /* The line only had one entry */
+            max = min;
+        }
+        else if (max < min) {
+            if (SvCUR(msg) > 0) sv_catpvs(msg, "; ");
+            sv_catpvs(msg, "Illegal range in \"");
+            Perl_sv_catpvf(aTHX_ msg, "%" UTF8f,
+                                UTF8fARG(is_contents_utf8, s - s0, s0));
+            sv_catpvs(msg, "\"");
+            goto return_failure;
+        }
+
+#if 0   /* See explanation at definition above of get_extended_utf8_msg() */
+
+        if (   UNICODE_IS_PERL_EXTENDED(min)
+            || UNICODE_IS_PERL_EXTENDED(max))
+        {
+            if (SvCUR(msg) > 0) sv_catpvs(msg, "; ");
+
+            /* If both code points are non-portable, warn only on the lower
+             * one. */
+            sv_catpv(msg, get_extended_utf8_msg(
+                                            (UNICODE_IS_PERL_EXTENDED(min))
+                                            ? min : max));
+            sv_catpvs(msg, " in \"");
+            Perl_sv_catpvf(aTHX_ msg, "%" UTF8f,
+                                 UTF8fARG(is_contents_utf8, s - s0, s0));
+            sv_catpvs(msg, "\"");
+        }
+
+#endif
+
+        /* Here, this line contains a legal range */
+        this_definition = sv_2mortal(_new_invlist(2));
+        this_definition = _add_range_to_invlist(this_definition, min, max);
+        goto calculate;
+
+      check_if_property:
+
+        /* Here it isn't a legal range line.  See if it is a legal property
+         * line.  First find the end of the meat of the line */
+        s = strpbrk(s, "#\n");
+        if (s == NULL) {
+            s = e;
+        }
+
+        /* Ignore trailing blanks in keeping with the requirements of
+         * parse_uniprop_string() */
+        s--;
+        while (s > s0 && isBLANK_A(*s)) {
+            s--;
+        }
+        s++;
+
+        this_definition = parse_uniprop_string(s0, s - s0,
+                                               is_utf8, to_fold, runtime,
+                                               deferrable,
+                                               user_defined_ptr, msg,
+                                               (name_len == 0)
+                                                ? level /* Don't increase level
+                                                           if input is empty */
+                                                : level + 1
+                                              );
+        if (this_definition == NULL) {
+            goto return_failure;    /* 'msg' should have had the reason
+                                       appended to it by the above call */
+        }
+
+        if (! is_invlist(this_definition)) {    /* Unknown at this time */
+            return newSVsv(this_definition);
+        }
+
+        if (*s != '\n') {
+            s = strchr(s, '\n');
+            if (s == NULL) {
+                s = e;
+            }
+        }
+
+      calculate:
+
+        switch (op) {
+            case '+':
+                _invlist_union(running_definition, this_definition,
+                                                        &running_definition);
+                break;
+            case '-':
+                _invlist_subtract(running_definition, this_definition,
+                                                        &running_definition);
+                break;
+            case '&':
+                _invlist_intersection(running_definition, this_definition,
+                                                        &running_definition);
+                break;
+            case '!':
+                _invlist_union_complement_2nd(running_definition,
+                                        this_definition, &running_definition);
+                break;
+            default:
+                Perl_croak(aTHX_ "panic: %s: %d: Unexpected operation %d",
+                                 __FILE__, __LINE__, op);
+                break;
+        }
+
+        /* Position past the '\n' */
+        s0 = s + 1;
+    }   /* End of loop through the lines of 'contents' */
+
+    /* Here, we processed all the lines in 'contents' without error.  If we
+     * didn't add any warnings, simply return success */
+    if (msgs_length_on_entry == SvCUR(msg)) {
+
+        /* If the expansion was empty, the answer isn't nothing: its an empty
+         * inversion list */
+        if (running_definition == NULL) {
+            running_definition = _new_invlist(1);
+        }
+
+        return running_definition;
+    }
+
+    /* Otherwise, add some explanatory text, but we will return success */
+    goto return_msg;
+
+  return_failure:
+    running_definition = NULL;
+
+  return_msg:
+
+    if (name_len > 0) {
+        sv_catpvs(msg, " in expansion of ");
+        Perl_sv_catpvf(aTHX_ msg, "%" UTF8f, UTF8fARG(is_utf8, name_len, name));
+    }
+
+    return running_definition;
+}
+
+/* As explained below, certain operations need to take place in the first
+ * thread created.  These macros switch contexts */
+#ifdef USE_ITHREADS
+#  define DECLARATION_FOR_GLOBAL_CONTEXT                                    \
+                                        PerlInterpreter * save_aTHX = aTHX;
+#  define SWITCH_TO_GLOBAL_CONTEXT                                          \
+                           PERL_SET_CONTEXT((aTHX = PL_user_def_props_aTHX))
+#  define RESTORE_CONTEXT  PERL_SET_CONTEXT((aTHX = save_aTHX));
+#  define CUR_CONTEXT      aTHX
+#  define ORIGINAL_CONTEXT save_aTHX
+#else
+#  define DECLARATION_FOR_GLOBAL_CONTEXT
+#  define SWITCH_TO_GLOBAL_CONTEXT          NOOP
+#  define RESTORE_CONTEXT                   NOOP
+#  define CUR_CONTEXT                       NULL
+#  define ORIGINAL_CONTEXT                  NULL
+#endif
+
+STATIC void
+S_delete_recursion_entry(pTHX_ void *key)
+{
+    /* Deletes the entry used to detect recursion when expanding user-defined
+     * properties.  This is a function so it can be set up to be called even if
+     * the program unexpectedly quits */
+
+    dVAR;
+    SV ** current_entry;
+    const STRLEN key_len = strlen((const char *) key);
+    DECLARATION_FOR_GLOBAL_CONTEXT;
+
+    SWITCH_TO_GLOBAL_CONTEXT;
+
+    /* If the entry is one of these types, it is a permanent entry, and not the
+     * one used to detect recursions.  This function should delete only the
+     * recursion entry */
+    current_entry = hv_fetch(PL_user_def_props, (const char *) key, key_len, 0);
+    if (     current_entry
+        && ! is_invlist(*current_entry)
+        && ! SvPOK(*current_entry))
+    {
+        (void) hv_delete(PL_user_def_props, (const char *) key, key_len,
+                                                                    G_DISCARD);
+    }
+
+    RESTORE_CONTEXT;
+}
+
+STATIC SV *
+S_get_fq_name(pTHX_
+              const char * const name,    /* The first non-blank in the \p{}, \P{} */
+              const Size_t name_len,      /* Its length in bytes, not including any trailing space */
+              const bool is_utf8,         /* ? Is 'name' encoded in UTF-8 */
+              const bool has_colon_colon
+             )
+{
+    /* Returns a mortal SV containing the fully qualified version of the input
+     * name */
+
+    SV * fq_name;
+
+    fq_name = newSVpvs_flags("", SVs_TEMP);
+
+    /* Use the current package if it wasn't included in our input */
+    if (! has_colon_colon) {
+        const HV * pkg = (IN_PERL_COMPILETIME)
+                         ? PL_curstash
+                         : CopSTASH(PL_curcop);
+        const char* pkgname = HvNAME(pkg);
+
+        Perl_sv_catpvf(aTHX_ fq_name, "%" UTF8f,
+                      UTF8fARG(is_utf8, strlen(pkgname), pkgname));
+        sv_catpvs(fq_name, "::");
+    }
+
+    Perl_sv_catpvf(aTHX_ fq_name, "%" UTF8f,
+                         UTF8fARG(is_utf8, name_len, name));
+    return fq_name;
+}
+
+SV *
+Perl_parse_uniprop_string(pTHX_
+
+    /* Parse the interior of a \p{}, \P{}.  Returns its definition if knowable
+     * now.  If so, the return is an inversion list.
+     *
+     * If the property is user-defined, it is a subroutine, which in turn
+     * may call other subroutines.  This function will call the whole nest of
+     * them to get the definition they return; if some aren't known at the time
+     * of the call to this function, the fully qualified name of the highest
+     * level sub is returned.  It is an error to call this function at runtime
+     * without every sub defined.
+     *
+     * If an error was found, NULL is returned, and 'msg' gets a suitable
+     * message appended to it.  (Appending allows the back trace of how we got
+     * to the faulty definition to be displayed through nested calls of
+     * user-defined subs.)
+     *
+     * The caller should NOT try to free any returned inversion list.
+     *
+     * Other parameters will be set on return as described below */
+
+    const char * const name,    /* The first non-blank in the \p{}, \P{} */
+    const Size_t name_len,      /* Its length in bytes, not including any
+                                   trailing space */
+    const bool is_utf8,         /* ? Is 'name' encoded in UTF-8 */
+    const bool to_fold,         /* ? Is this under /i */
+    const bool runtime,         /* TRUE if this is being called at run time */
+    const bool deferrable,      /* TRUE if it's ok for the definition to not be
+                                   known at this call */
+    bool *user_defined_ptr,     /* Upon return from this function it will be
+                                   set to TRUE if any component is a
+                                   user-defined property */
+    SV * msg,                   /* Any error or warning msg(s) are appended to
+                                   this */
+   const STRLEN level)          /* Recursion level of this call */
+{
+    dVAR;
+    char* lookup_name;          /* normalized name for lookup in our tables */
+    unsigned lookup_len;        /* Its length */
+    bool stricter = FALSE;      /* Some properties have stricter name
+                                   normalization rules, which we decide upon
+                                   based on parsing */
+
+    /* nv= or numeric_value=, or possibly one of the cjk numeric properties
+     * (though it requires extra effort to download them from Unicode and
+     * compile perl to know about them) */
+    bool is_nv_type = FALSE;
+
+    unsigned int i, j = 0;
+    int equals_pos = -1;    /* Where the '=' is found, or negative if none */
+    int slash_pos  = -1;    /* Where the '/' is found, or negative if none */
+    int table_index = 0;    /* The entry number for this property in the table
+                               of all Unicode property names */
+    bool starts_with_Is = FALSE;  /* ? Does the name start with 'Is' */
+    Size_t lookup_offset = 0;   /* Used to ignore the first few characters of
+                                   the normalized name in certain situations */
+    Size_t non_pkg_begin = 0;   /* Offset of first byte in 'name' that isn't
+                                   part of a package name */
+    bool could_be_user_defined = TRUE;  /* ? Could this be a user-defined
+                                             property rather than a Unicode
+                                             one. */
+    SV * prop_definition = NULL;  /* The returned definition of 'name' or NULL
+                                     if an error.  If it is an inversion list,
+                                     it is the definition.  Otherwise it is a
+                                     string containing the fully qualified sub
+                                     name of 'name' */
+    SV * fq_name = NULL;        /* For user-defined properties, the fully
+                                   qualified name */
+    bool invert_return = FALSE; /* ? Do we need to complement the result before
+                                     returning it */
 
     PERL_ARGS_ASSERT_PARSE_UNIPROP_STRING;
 
-    /* The input will be modified into 'lookup_name' */
+    /* The input will be normalized into 'lookup_name' */
     Newx(lookup_name, name_len, char);
     SAVEFREEPV(lookup_name);
 
@@ -21497,40 +22685,86 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
     for (i = 0; i < name_len; i++) {
         char cur = name[i];
 
-        /* These characters can be freely ignored in most situations.  Later it
-         * may turn out we shouldn't have ignored them, and we have to reparse,
-         * but we don't have enough information yet to make that decision */
-        if (cur == '-' || cur == '_' || isSPACE_A(cur)) {
+        /* Most of the characters in the input will be of this ilk, being parts
+         * of a name */
+        if (isIDCONT_A(cur)) {
+
+            /* Case differences are ignored.  Our lookup routine assumes
+             * everything is lowercase, so normalize to that */
+            if (isUPPER_A(cur)) {
+                lookup_name[j++] = toLOWER_A(cur);
+                continue;
+            }
+
+            if (cur == '_') { /* Don't include these in the normalized name */
+                continue;
+            }
+
+            lookup_name[j++] = cur;
+
+            /* The first character in a user-defined name must be of this type.
+             * */
+            if (i - non_pkg_begin == 0 && ! isIDFIRST_A(cur)) {
+                could_be_user_defined = FALSE;
+            }
+
             continue;
         }
 
-        /* Case differences are also ignored.  Our lookup routine assumes
-         * everything is lowercase */
-        if (isUPPER_A(cur)) {
-            lookup_name[j++] = toLOWER(cur);
+        /* Here, the character is not something typically in a name,  But these
+         * two types of characters (and the '_' above) can be freely ignored in
+         * most situations.  Later it may turn out we shouldn't have ignored
+         * them, and we have to reparse, but we don't have enough information
+         * yet to make that decision */
+        if (cur == '-' || isSPACE_A(cur)) {
+            could_be_user_defined = FALSE;
             continue;
         }
 
-        /* A double colon is either an error, or a package qualifier to a
-         * subroutine user-defined property; neither of which do we currently
-         * handle
-         *
-         * But a single colon is a synonym for '=' */
-        if (cur == ':') {
-            if (i < name_len - 1 && name[i+1] == ':') {
-                return NULL;
-            }
-            cur = '=';
+        /* An equals sign or single colon mark the end of the first part of
+         * the property name */
+        if (    cur == '='
+            || (cur == ':' && (i >= name_len - 1 || name[i+1] != ':')))
+        {
+            lookup_name[j++] = '='; /* Treat the colon as an '=' */
+            equals_pos = j; /* Note where it occurred in the input */
+            could_be_user_defined = FALSE;
+            break;
         }
 
         /* Otherwise, this character is part of the name. */
         lookup_name[j++] = cur;
 
-        /* Only the equals sign needs further processing */
-        if (cur == '=') {
-            equals_pos = j; /* Note where it occurred in the input */
-            break;
+        /* Here it isn't a single colon, so if it is a colon, it must be a
+         * double colon */
+        if (cur == ':') {
+
+            /* A double colon should be a package qualifier.  We note its
+             * position and continue.  Note that one could have
+             *      pkg1::pkg2::...::foo
+             * so that the position at the end of the loop will be just after
+             * the final qualifier */
+
+            i++;
+            non_pkg_begin = i + 1;
+            lookup_name[j++] = ':';
+        }
+        else { /* Only word chars (and '::') can be in a user-defined name */
+            could_be_user_defined = FALSE;
         }
+    } /* End of parsing through the lhs of the property name (or all of it if
+         no rhs) */
+
+#define STRLENs(s)  (sizeof("" s "") - 1)
+
+    /* If there is a single package name 'utf8::', it is ambiguous.  It could
+     * be for a user-defined property, or it could be a Unicode property, as
+     * all of them are considered to be for that package.  For the purposes of
+     * parsing the rest of the property, strip it off */
+    if (non_pkg_begin == STRLENs("utf8::") && memBEGINPs(name, name_len, "utf8::")) {
+        lookup_name +=  STRLENs("utf8::");
+        j -=  STRLENs("utf8::");
+        equals_pos -=  STRLENs("utf8::");
     }
 
     /* Here, we are either done with the whole property name, if it was simple;
@@ -21547,17 +22781,185 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
             }
         }
 
-        /* Certain properties need special handling.  They may optionally be
-         * prefixed by 'is'.  Ignore that prefix for the purposes of checking
-         * if this is one of those properties */
-        if (memBEGINPs(lookup_name, name_len, "is")) {
+        /* Most punctuation after the equals indicates a subpattern, like
+         * \p{foo=/bar/} */
+        if (   isPUNCT_A(name[i])
+            && name[i] != '-'
+            && name[i] != '+'
+            && name[i] != '_'
+            && name[i] != '{')
+        {
+            /* Find the property.  The table includes the equals sign, so we
+             * use 'j' as-is */
+            table_index = match_uniprop((U8 *) lookup_name, j);
+            if (table_index) {
+                const char * const * prop_values
+                                            = UNI_prop_value_ptrs[table_index];
+                SV * subpattern;
+                Size_t subpattern_len;
+                REGEXP * subpattern_re;
+                char open = name[i++];
+                char close;
+                const char * pos_in_brackets;
+                bool escaped = 0;
+
+                /* A backslash means the real delimitter is the next character.
+                 * */
+                if (open == '\\') {
+                    open = name[i++];
+                    escaped = 1;
+                }
+
+                /* This data structure is constructed so that the matching
+                 * closing bracket is 3 past its matching opening.  The second
+                 * set of closing is so that if the opening is something like
+                 * ']', the closing will be that as well.  Something similar is
+                 * done in toke.c */
+                pos_in_brackets = strchr("([<)]>)]>", open);
+                close = (pos_in_brackets) ? pos_in_brackets[3] : open;
+
+                if (    i >= name_len
+                    ||  name[name_len-1] != close
+                    || (escaped && name[name_len-2] != '\\'))
+                {
+                    sv_catpvs(msg, "Unicode property wildcard not terminated");
+                    goto append_name_to_msg;
+                }
+
+                Perl_ck_warner_d(aTHX_
+                    packWARN(WARN_EXPERIMENTAL__UNIPROP_WILDCARDS),
+                    "The Unicode property wildcards feature is experimental");
+
+                /* Now create and compile the wildcard subpattern.  Use /iaa
+                 * because nothing outside of ASCII will match, and it the
+                 * property values should all match /i.  Note that when the
+                 * pattern fails to compile, our added text to the user's
+                 * pattern will be displayed to the user, which is not so
+                 * desirable. */
+                subpattern_len = name_len - i - 1 - escaped;
+                subpattern = Perl_newSVpvf(aTHX_ "(?iaa:%.*s)",
+                                              (unsigned) subpattern_len,
+                                              name + i);
+                subpattern = sv_2mortal(subpattern);
+                subpattern_re = re_compile(subpattern, 0);
+                assert(subpattern_re);  /* Should have died if didn't compile
+                                         successfully */
+
+                /* For each legal property value, see if the supplied pattern
+                 * matches it. */
+                while (*prop_values) {
+                    const char * const entry = *prop_values;
+                    const Size_t len = strlen(entry);
+                    SV* entry_sv = newSVpvn_flags(entry, len, SVs_TEMP);
+
+                    if (pregexec(subpattern_re,
+                                 (char *) entry,
+                                 (char *) entry + len,
+                                 (char *) entry, 0,
+                                 entry_sv,
+                                 0))
+                    { /* Here, matched.  Add to the returned list */
+                        Size_t total_len = j + len;
+                        SV * sub_invlist = NULL;
+                        char * this_string;
+
+                        /* We know this is a legal \p{property=value}.  Call
+                         * the function to return the list of code points that
+                         * match it */
+                        Newxz(this_string, total_len + 1, char);
+                        Copy(lookup_name, this_string, j, char);
+                        my_strlcat(this_string, entry, total_len + 1);
+                        SAVEFREEPV(this_string);
+                        sub_invlist = parse_uniprop_string(this_string,
+                                                           total_len,
+                                                           is_utf8,
+                                                           to_fold,
+                                                           runtime,
+                                                           deferrable,
+                                                           user_defined_ptr,
+                                                           msg,
+                                                           level + 1);
+                        _invlist_union(prop_definition, sub_invlist,
+                                       &prop_definition);
+                    }
+
+                    prop_values++;  /* Next iteration, look at next propvalue */
+                } /* End of looking through property values; (the data
+                     structure is terminated by a NULL ptr) */
+
+                SvREFCNT_dec_NN(subpattern_re);
+
+                if (prop_definition) {
+                    return prop_definition;
+                }
+
+                sv_catpvs(msg, "No Unicode property value wildcard matches:");
+                goto append_name_to_msg;
+            }
+
+            /* Here's how khw thinks we should proceed to handle the properties
+             * not yet done:    Bidi Mirroring Glyph
+                                Bidi Paired Bracket
+                                Case Folding  (both full and simple)
+                                Decomposition Mapping
+                                Equivalent Unified Ideograph
+                                Name
+                                Name Alias
+                                Lowercase Mapping  (both full and simple)
+                                NFKC Case Fold
+                                Titlecase Mapping  (both full and simple)
+                                Uppercase Mapping  (both full and simple)
+             * Move the part that looks at the property values into a perl
+             * script, like utf8_heavy.pl is done.  This makes things somewhat
+             * easier, but most importantly, it avoids always adding all these
+             * strings to the memory usage when the feature is little-used.
+             *
+             * The property values would all be concatenated into a single
+             * string per property with each value on a separate line, and the
+             * code point it's for on alternating lines.  Then we match the
+             * user's input pattern m//mg, without having to worry about their
+             * uses of '^' and '$'.  Only the values that aren't the default
+             * would be in the strings.  Code points would be in UTF-8.  The
+             * search pattern that we would construct would look like
+             * (?: \n (code-point_re) \n (?aam: user-re ) \n )
+             * And so $1 would contain the code point that matched the user-re.
+             * For properties where the default is the code point itself, such
+             * as any of the case changing mappings, the string would otherwise
+             * consist of all Unicode code points in UTF-8 strung together.
+             * This would be impractical.  So instead, examine their compiled
+             * pattern, looking at the ssc.  If none, reject the pattern as an
+             * error.  Otherwise run the pattern against every code point in
+             * the ssc.  The ssc is kind of like tr18's 3.9 Possible Match Sets
+             * And it might be good to create an API to return the ssc.
+             *
+             * For the name properties, a new function could be created in
+             * charnames which essentially does the same thing as above,
+             * sharing Name.pl with the other charname functions.  Don't know
+             * about loose name matching, or algorithmically determined names.
+             * Decomposition.pl similarly.
+             *
+             * It might be that a new pattern modifier would have to be
+             * created, like /t for resTricTed, which changed the behavior of
+             * some constructs in their subpattern, like \A. */
+        } /* End of is a wildcard subppattern */
+
+
+        /* Certain properties whose values are numeric need special handling.
+         * They may optionally be prefixed by 'is'.  Ignore that prefix for the
+         * purposes of checking if this is one of those properties */
+        if (memBEGINPs(lookup_name, j, "is")) {
             lookup_offset = 2;
         }
 
-        /* Then check if it is one of these properties.  This is hard-coded
-         * because easier this way, and the list is unlikely to change.  There
-         * are several properties like this in the Unihan DB, which is unlikely
-         * to be compiled, and they all end with 'numeric'.  The interiors
+        /* Then check if it is one of these specially-handled properties.  The
+         * possibilities are hard-coded because easier this way, and the list
+         * is unlikely to change.
+         *
+         * All numeric value type properties are of this ilk, and are also
+         * special in a different way later on.  So find those first.  There
+         * are several numeric value type properties in the Unihan DB (which is
+         * unlikely to be compiled with perl, but we handle it here in case it
+         * does get compiled).  They all end with 'numeric'.  The interiors
          * aren't checked for the precise property.  This would stop working if
          * a cjk property were to be created that ended with 'numeric' and
          * wasn't a numeric type */
@@ -21585,15 +22987,14 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
         {
             unsigned int k;
 
-            /* What makes these properties special is that the stuff after the
-             * '=' is a number.  Therefore, we can't throw away '-'
-             * willy-nilly, as those could be a minus sign.  Other stricter
+            /* Since the stuff after the '=' is a number, we can't throw away
+             * '-' willy-nilly, as those could be a minus sign.  Other stricter
              * rules also apply.  However, these properties all can have the
              * rhs not be a number, in which case they contain at least one
              * alphabetic.  In those cases, the stricter rules don't apply.
              * But the numeric type properties can have the alphas [Ee] to
              * signify an exponent, and it is still a number with stricter
-             * rules.  So look for an alpha that signifys not-strict */
+             * rules.  So look for an alpha that signifies not-strict */
             stricter = TRUE;
             for (k = i; k < name_len; k++) {
                 if (   isALPHA_A(name[k])
@@ -21621,7 +23022,7 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
              * zeros, or between the final leading zero and the first other
              * digit */
             for (; i < name_len - 1; i++) {
-                if (   name[i] != '0'
+                if (    name[i] != '0'
                     && (name[i] != '_' || ! isDIGIT_A(name[i+1])))
                 {
                     break;
@@ -21631,9 +23032,8 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
     }
     else {  /* No '=' */
 
-       /* We are now in a position to determine if this property should have
-        * been parsed using stricter rules.  Only a few are like that, and
-        * unlikely to change. */
+       /* Only a few properties without an '=' should be parsed with stricter
+        * rules.  The list is unlikely to change. */
         if (   memBEGINPs(lookup_name, j, "perl")
             && memNEs(lookup_name + 4, j - 4, "space")
             && memNEs(lookup_name + 4, j - 4, "word"))
@@ -21713,7 +23113,9 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
             }
 
             /* Store the first real character in the denominator */
-            lookup_name[j++] = name[i];
+            if (i < name_len) {
+                lookup_name[j++] = name[i];
+            }
         }
     }
 
@@ -21728,34 +23130,361 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
     {
         lookup_name[j++] = '&';
     }
-    else if (name_len > 2 && name[0] == 'I' && (   name[1] == 'n'
-                                                || name[1] == 's'))
-    {
 
-        /* Also, if the original input began with 'In' or 'Is', it could be a
-         * subroutine call instead of a property names, which currently isn't
-         * handled by this function.  Subroutine calls can't happen if there is
-         * an '=' in the name */
-        if (equals_pos < 0 && get_cvn_flags(name, name_len, GV_NOTQUAL) != NULL)
-        {
-            return NULL;
+    /* If the original input began with 'In' or 'Is', it could be a subroutine
+     * call to a user-defined property instead of a Unicode property name. */
+    if (    name_len - non_pkg_begin > 2
+        &&  name[non_pkg_begin+0] == 'I'
+        && (name[non_pkg_begin+1] == 'n' || name[non_pkg_begin+1] == 's'))
+    {
+        /* Names that start with In have different characterstics than those
+         * that start with Is */
+        if (name[non_pkg_begin+1] == 's') {
+            starts_with_Is = TRUE;
         }
-
-        starts_with_In_or_Is = TRUE;
     }
+    else {
+        could_be_user_defined = FALSE;
+    }
+
+    if (could_be_user_defined) {
+        CV* user_sub;
+
+        /* If the user defined property returns the empty string, it could
+         * easily be because the pattern is being compiled before the data it
+         * actually needs to compile is available.  This could be argued to be
+         * a bug in the perl code, but this is a change of behavior for Perl,
+         * so we handle it.  This means that intentionally returning nothing
+         * will not be resolved until runtime */
+        bool empty_return = FALSE;
+
+        /* Here, the name could be for a user defined property, which are
+         * implemented as subs. */
+        user_sub = get_cvn_flags(name, name_len, 0);
+        if (user_sub) {
+            const char insecure[] = "Insecure user-defined property";
+
+            /* Here, there is a sub by the correct name.  Normally we call it
+             * to get the property definition */
+            dSP;
+            SV * user_sub_sv = MUTABLE_SV(user_sub);
+            SV * error;     /* Any error returned by calling 'user_sub' */
+            SV * key;       /* The key into the hash of user defined sub names
+                             */
+            SV * placeholder;
+            SV ** saved_user_prop_ptr;      /* Hash entry for this property */
+
+            /* How many times to retry when another thread is in the middle of
+             * expanding the same definition we want */
+            PERL_INT_FAST8_T retry_countdown = 10;
+
+            DECLARATION_FOR_GLOBAL_CONTEXT;
+
+            /* If we get here, we know this property is user-defined */
+            *user_defined_ptr = TRUE;
+
+            /* We refuse to call a potentially tainted subroutine; returning an
+             * error instead */
+            if (TAINT_get) {
+                if (SvCUR(msg) > 0) sv_catpvs(msg, "; ");
+                sv_catpvn(msg, insecure, sizeof(insecure) - 1);
+                goto append_name_to_msg;
+            }
+
+            /* In principal, we only call each subroutine property definition
+             * once during the life of the program.  This guarantees that the
+             * property definition never changes.  The results of the single
+             * sub call are stored in a hash, which is used instead for future
+             * references to this property.  The property definition is thus
+             * immutable.  But, to allow the user to have a /i-dependent
+             * definition, we call the sub once for non-/i, and once for /i,
+             * should the need arise, passing the /i status as a parameter.
+             *
+             * We start by constructing the hash key name, consisting of the
+             * fully qualified subroutine name, preceded by the /i status, so
+             * that there is a key for /i and a different key for non-/i */
+            key = newSVpvn(((to_fold) ? "1" : "0"), 1);
+            fq_name = S_get_fq_name(aTHX_ name, name_len, is_utf8,
+                                          non_pkg_begin != 0);
+            sv_catsv(key, fq_name);
+            sv_2mortal(key);
+
+            /* We only call the sub once throughout the life of the program
+             * (with the /i, non-/i exception noted above).  That means the
+             * hash must be global and accessible to all threads.  It is
+             * created at program start-up, before any threads are created, so
+             * is accessible to all children.  But this creates some
+             * complications.
+             *
+             * 1) The keys can't be shared, or else problems arise; sharing is
+             *    turned off at hash creation time
+             * 2) All SVs in it are there for the remainder of the life of the
+             *    program, and must be created in the same interpreter context
+             *    as the hash, or else they will be freed from the wrong pool
+             *    at global destruction time.  This is handled by switching to
+             *    the hash's context to create each SV going into it, and then
+             *    immediately switching back
+             * 3) All accesses to the hash must be controlled by a mutex, to
+             *    prevent two threads from getting an unstable state should
+             *    they simultaneously be accessing it.  The code below is
+             *    crafted so that the mutex is locked whenever there is an
+             *    access and unlocked only when the next stable state is
+             *    achieved.
+             *
+             * The hash stores either the definition of the property if it was
+             * valid, or, if invalid, the error message that was raised.  We
+             * use the type of SV to distinguish.
+             *
+             * There's also the need to guard against the definition expansion
+             * from infinitely recursing.  This is handled by storing the aTHX
+             * of the expanding thread during the expansion.  Again the SV type
+             * is used to distinguish this from the other two cases.  If we
+             * come to here and the hash entry for this property is our aTHX,
+             * it means we have recursed, and the code assumes that we would
+             * infinitely recurse, so instead stops and raises an error.
+             * (Any recursion has always been treated as infinite recursion in
+             * this feature.)
+             *
+             * If instead, the entry is for a different aTHX, it means that
+             * that thread has gotten here first, and hasn't finished expanding
+             * the definition yet.  We just have to wait until it is done.  We
+             * sleep and retry a few times, returning an error if the other
+             * thread doesn't complete. */
+
+          re_fetch:
+            USER_PROP_MUTEX_LOCK;
+
+            /* If we have an entry for this key, the subroutine has already
+             * been called once with this /i status. */
+            saved_user_prop_ptr = hv_fetch(PL_user_def_props,
+                                                   SvPVX(key), SvCUR(key), 0);
+            if (saved_user_prop_ptr) {
+
+                /* If the saved result is an inversion list, it is the valid
+                 * definition of this property */
+                if (is_invlist(*saved_user_prop_ptr)) {
+                    prop_definition = *saved_user_prop_ptr;
+
+                    /* The SV in the hash won't be removed until global
+                     * destruction, so it is stable and we can unlock */
+                    USER_PROP_MUTEX_UNLOCK;
+
+                    /* The caller shouldn't try to free this SV */
+                    return prop_definition;
+                }
+
+                /* Otherwise, if it is a string, it is the error message
+                 * that was returned when we first tried to evaluate this
+                 * property.  Fail, and append the message */
+                if (SvPOK(*saved_user_prop_ptr)) {
+                    if (SvCUR(msg) > 0) sv_catpvs(msg, "; ");
+                    sv_catsv(msg, *saved_user_prop_ptr);
+
+                    /* The SV in the hash won't be removed until global
+                     * destruction, so it is stable and we can unlock */
+                    USER_PROP_MUTEX_UNLOCK;
 
-    lookup_len = j;     /* Use a more mnemonic name starting here */
+                    return NULL;
+                }
+
+                assert(SvIOK(*saved_user_prop_ptr));
+
+                /* Here, we have an unstable entry in the hash.  Either another
+                 * thread is in the middle of expanding the property's
+                 * definition, or we are ourselves recursing.  We use the aTHX
+                 * in it to distinguish */
+                if (SvIV(*saved_user_prop_ptr) != PTR2IV(CUR_CONTEXT)) {
+
+                    /* Here, it's another thread doing the expanding.  We've
+                     * looked as much as we are going to at the contents of the
+                     * hash entry.  It's safe to unlock. */
+                    USER_PROP_MUTEX_UNLOCK;
+
+                    /* Retry a few times */
+                    if (retry_countdown-- > 0) {
+                        PerlProc_sleep(1);
+                        goto re_fetch;
+                    }
+
+                    if (SvCUR(msg) > 0) sv_catpvs(msg, "; ");
+                    sv_catpvs(msg, "Timeout waiting for another thread to "
+                                   "define");
+                    goto append_name_to_msg;
+                }
+
+                /* Here, we are recursing; don't dig any deeper */
+                USER_PROP_MUTEX_UNLOCK;
+
+                if (SvCUR(msg) > 0) sv_catpvs(msg, "; ");
+                sv_catpvs(msg,
+                          "Infinite recursion in user-defined property");
+                goto append_name_to_msg;
+            }
+
+            /* Here, this thread has exclusive control, and there is no entry
+             * for this property in the hash.  So we have the go ahead to
+             * expand the definition ourselves. */
+
+            PUSHSTACKi(PERLSI_MAGIC);
+            ENTER;
+
+            /* Create a temporary placeholder in the hash to detect recursion
+             * */
+            SWITCH_TO_GLOBAL_CONTEXT;
+            placeholder= newSVuv(PTR2IV(ORIGINAL_CONTEXT));
+            (void) hv_store_ent(PL_user_def_props, key, placeholder, 0);
+            RESTORE_CONTEXT;
+
+            /* Now that we have a placeholder, we can let other threads
+             * continue */
+            USER_PROP_MUTEX_UNLOCK;
+
+            /* Make sure the placeholder always gets destroyed */
+            SAVEDESTRUCTOR_X(S_delete_recursion_entry, SvPVX(key));
+
+            PUSHMARK(SP);
+            SAVETMPS;
+
+            /* Call the user's function, with the /i status as a parameter.
+             * Note that we have gone to a lot of trouble to keep this call
+             * from being within the locked mutex region. */
+            XPUSHs(boolSV(to_fold));
+            PUTBACK;
+
+            /* The following block was taken from swash_init().  Presumably
+             * they apply to here as well, though we no longer use a swash --
+             * khw */
+            SAVEHINTS();
+            save_re_context();
+            /* We might get here via a subroutine signature which uses a utf8
+             * parameter name, at which point PL_subname will have been set
+             * but not yet used. */
+            save_item(PL_subname);
+
+            (void) call_sv(user_sub_sv, G_EVAL|G_SCALAR);
+
+            SPAGAIN;
+
+            error = ERRSV;
+            if (TAINT_get || SvTRUE(error)) {
+                if (SvCUR(msg) > 0) sv_catpvs(msg, "; ");
+                if (SvTRUE(error)) {
+                    sv_catpvs(msg, "Error \"");
+                    sv_catsv(msg, error);
+                    sv_catpvs(msg, "\"");
+                }
+                if (TAINT_get) {
+                    if (SvTRUE(error)) sv_catpvs(msg, "; ");
+                    sv_catpvn(msg, insecure, sizeof(insecure) - 1);
+                }
+
+                if (name_len > 0) {
+                    sv_catpvs(msg, " in expansion of ");
+                    Perl_sv_catpvf(aTHX_ msg, "%" UTF8f, UTF8fARG(is_utf8,
+                                                                  name_len,
+                                                                  name));
+                }
+
+                (void) POPs;
+                prop_definition = NULL;
+            }
+            else {  /* G_SCALAR guarantees a single return value */
+                SV * contents = POPs;
+
+                /* The contents is supposed to be the expansion of the property
+                 * definition.  If the definition is deferrable, and we got an
+                 * empty string back, set a flag to later defer it (after clean
+                 * up below). */
+                if (      deferrable
+                    && (! SvPOK(contents) || SvCUR(contents) == 0))
+                {
+                        empty_return = TRUE;
+                }
+                else { /* Otherwise, call a function to check for valid syntax,
+                          and handle it */
+
+                    prop_definition = handle_user_defined_property(
+                                                    name, name_len,
+                                                    is_utf8, to_fold, runtime,
+                                                    deferrable,
+                                                    contents, user_defined_ptr,
+                                                    msg,
+                                                    level);
+                }
+            }
+
+            /* Here, we have the results of the expansion.  Delete the
+             * placeholder, and if the definition is now known, replace it with
+             * that definition.  We need exclusive access to the hash, and we
+             * can't let anyone else in, between when we delete the placeholder
+             * and add the permanent entry */
+            USER_PROP_MUTEX_LOCK;
+
+            S_delete_recursion_entry(aTHX_ SvPVX(key));
+
+            if (    ! empty_return
+                && (! prop_definition || is_invlist(prop_definition)))
+            {
+                /* If we got success we use the inversion list defining the
+                 * property; otherwise use the error message */
+                SWITCH_TO_GLOBAL_CONTEXT;
+                (void) hv_store_ent(PL_user_def_props,
+                                    key,
+                                    ((prop_definition)
+                                     ? newSVsv(prop_definition)
+                                     : newSVsv(msg)),
+                                    0);
+                RESTORE_CONTEXT;
+            }
+
+            /* All done, and the hash now has a permanent entry for this
+             * property.  Give up exclusive control */
+            USER_PROP_MUTEX_UNLOCK;
+
+            FREETMPS;
+            LEAVE;
+            POPSTACK;
+
+            if (empty_return) {
+                goto definition_deferred;
+            }
+
+            if (prop_definition) {
+
+                /* If the definition is for something not known at this time,
+                 * we toss it, and go return the main property name, as that's
+                 * the one the user will be aware of */
+                if (! is_invlist(prop_definition)) {
+                    SvREFCNT_dec_NN(prop_definition);
+                    goto definition_deferred;
+                }
+
+                sv_2mortal(prop_definition);
+            }
+
+            /* And return */
+            return prop_definition;
+
+        }   /* End of calling the subroutine for the user-defined property */
+    }       /* End of it could be a user-defined property */
+
+    /* Here it wasn't a user-defined property that is known at this time.  See
+     * if it is a Unicode property */
+
+    lookup_len = j;     /* This is a more mnemonic name than 'j' */
 
     /* Get the index into our pointer table of the inversion list corresponding
      * to the property */
     table_index = match_uniprop((U8 *) lookup_name, lookup_len);
 
-    /* If it didn't find the property */
+    /* If it didn't find the property ... */
     if (table_index == 0) {
 
-        /* If didn't find the property, we try again stripping off any initial
-         * 'In' or 'Is' */
-        if (starts_with_In_or_Is) {
+        /* Try again stripping off any initial 'Is'.  This is because we
+         * promise that an initial Is is optional.  The same isn't true of
+         * names that start with 'In'.  Those can match only blocks, and the
+         * lookup table already has those accounted for. */
+        if (starts_with_Is) {
             lookup_name += 2;
             lookup_len -= 2;
             equals_pos -= 2;
@@ -21767,14 +23496,28 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
         if (table_index == 0) {
             char * canonical;
 
-            /* If not found, and not a numeric type property, isn't a legal
-             * property */
+            /* Here, we didn't find it.  If not a numeric type property, and
+             * can't be a user-defined one, it isn't a legal property */
             if (! is_nv_type) {
-                return NULL;
-            }
+                if (! could_be_user_defined) {
+                    goto failed;
+                }
+
+                /* Here, the property name is legal as a user-defined one.   At
+                 * compile time, it might just be that the subroutine for that
+                 * property hasn't been encountered yet, but at runtime, it's
+                 * an error to try to use an undefined one */
+                if (! deferrable) {
+                    if (SvCUR(msg) > 0) sv_catpvs(msg, "; ");
+                    sv_catpvs(msg, "Unknown user-defined property name");
+                    goto append_name_to_msg;
+                }
+
+                goto definition_deferred;
+            } /* End of isn't a numeric type property */
 
-            /* But the numeric type properties need more work to decide.  What
-             * we do is make sure we have the number in canonical form and look
+            /* The numeric type properties need more work to decide.  What we
+             * do is make sure we have the number in canonical form and look
              * that up. */
 
             if (slash_pos < 0) {    /* No slash */
@@ -21784,19 +23527,22 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
                  * NV. */
 
                 NV value;
+                SSize_t value_len = lookup_len - equals_pos;
 
                 /* Get the value */
-                if (my_atof3(lookup_name + equals_pos, &value,
-                             lookup_len - equals_pos)
+                if (   value_len <= 0
+                    || my_atof3(lookup_name + equals_pos, &value,
+                                value_len)
                           != lookup_name + lookup_len)
                 {
-                    return NULL;
+                    goto failed;
                 }
 
-                /* If the value is an integer, the canonical value is integral */
+                /* If the value is an integer, the canonical value is integral
+                 * */
                 if (Perl_ceil(value) == value) {
                     canonical = Perl_form(aTHX_ "%.*s%.0" NVff,
-                                                equals_pos, lookup_name, value);
+                                            equals_pos, lookup_name, value);
                 }
                 else {  /* Otherwise, it is %e with a known precision */
                     char * exp_ptr;
@@ -21858,12 +23604,12 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
                 /* Convert the numerator to numeric */
                 end_ptr = this_lookup_name + slash_pos;
                 if (! grok_atoUV(this_lookup_name, &numerator, &end_ptr)) {
-                    return NULL;
+                    goto failed;
                 }
 
                 /* It better have included all characters before the slash */
                 if (*end_ptr != '/') {
-                    return NULL;
+                    goto failed;
                 }
 
                 /* Set to look at just the denominator */
@@ -21873,7 +23619,7 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
 
                 /* Convert the denominator to numeric */
                 if (! grok_atoUV(this_lookup_name, &denominator, &end_ptr)) {
-                    return NULL;
+                    goto failed;
                 }
 
                 /* It better be the rest of the characters, and don't divide by
@@ -21881,7 +23627,7 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
                 if (   end_ptr != this_lookup_name + lookup_len
                     || denominator == 0)
                 {
-                    return NULL;
+                    goto failed;
                 }
 
                 /* Get the greatest common denominator using
@@ -21897,11 +23643,11 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
                 /* If already in lowest possible terms, we have already tried
                  * looking this up */
                 if (gcd == 1) {
-                    return NULL;
+                    goto failed;
                 }
 
-                /* Reduce the rational, which should put it in canonical form.
-                 * Then look it up */
+                /* Reduce the rational, which should put it in canonical form
+                 * */
                 numerator /= gcd;
                 denominator /= gcd;
 
@@ -21912,26 +23658,23 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
             /* Here, we have the number in canonical form.  Try that */
             table_index = match_uniprop((U8 *) canonical, strlen(canonical));
             if (table_index == 0) {
-                return NULL;
+                goto failed;
             }
-        }
-    }
+        }   /* End of still didn't find the property in our table */
+    }       /* End of       didn't find the property in our table */
 
-    /* The return is an index into a table of ptrs.  A negative return
-     * signifies that the real index is the absolute value, but the result
-     * needs to be inverted */
+    /* Here, we have a non-zero return, which is an index into a table of ptrs.
+     * A negative return signifies that the real index is the absolute value,
+     * but the result needs to be inverted */
     if (table_index < 0) {
-        *invert = TRUE;
+        invert_return = TRUE;
         table_index = -table_index;
     }
-    else {
-        *invert = FALSE;
-    }
 
     /* Out-of band indices indicate a deprecated property.  The proper index is
      * modulo it with the table size.  And dividing by the table size yields
-     * an offset into a table constructed to contain the corresponding warning
-     * message */
+     * an offset into a table constructed by regen/mk_invlists.pl to contain
+     * the corresponding warning message */
     if (table_index > MAX_UNI_KEYWORD_INDEX) {
         Size_t warning_offset = table_index / MAX_UNI_KEYWORD_INDEX;
         table_index %= MAX_UNI_KEYWORD_INDEX;
@@ -21965,7 +23708,107 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
     }
 
     /* Create and return the inversion list */
-    return _new_invlist_C_array(uni_prop_ptrs[table_index]);
+    prop_definition =_new_invlist_C_array(uni_prop_ptrs[table_index]);
+    sv_2mortal(prop_definition);
+
+
+    /* See if there is a private use override to add to this definition */
+    {
+        COPHH * hinthash = (IN_PERL_COMPILETIME)
+                           ? CopHINTHASH_get(&PL_compiling)
+                           : CopHINTHASH_get(PL_curcop);
+       SV * pu_overrides = cophh_fetch_pv(hinthash, "private_use", 0, 0);
+
+        if (UNLIKELY(pu_overrides && SvPOK(pu_overrides))) {
+
+            /* See if there is an element in the hints hash for this table */
+            SV * pu_lookup = Perl_newSVpvf(aTHX_ "%d=", table_index);
+            const char * pos = strstr(SvPVX(pu_overrides), SvPVX(pu_lookup));
+
+            if (pos) {
+                bool dummy;
+                SV * pu_definition;
+                SV * pu_invlist;
+                SV * expanded_prop_definition =
+                            sv_2mortal(invlist_clone(prop_definition, NULL));
+
+                /* If so, it's definition is the string from here to the next
+                 * \a character.  And its format is the same as a user-defined
+                 * property */
+                pos += SvCUR(pu_lookup);
+                pu_definition = newSVpvn(pos, strchr(pos, '\a') - pos);
+                pu_invlist = handle_user_defined_property(lookup_name,
+                                                          lookup_len,
+                                                          0, /* Not UTF-8 */
+                                                          0, /* Not folded */
+                                                          runtime,
+                                                          deferrable,
+                                                          pu_definition,
+                                                          &dummy,
+                                                          msg,
+                                                          level);
+                if (TAINT_get) {
+                    if (SvCUR(msg) > 0) sv_catpvs(msg, "; ");
+                    sv_catpvs(msg, "Insecure private-use override");
+                    goto append_name_to_msg;
+                }
+
+                /* For now, as a safety measure, make sure that it doesn't
+                 * override non-private use code points */
+                _invlist_intersection(pu_invlist, PL_Private_Use, &pu_invlist);
+
+                /* Add it to the list to be returned */
+                _invlist_union(prop_definition, pu_invlist,
+                               &expanded_prop_definition);
+                prop_definition = expanded_prop_definition;
+                Perl_ck_warner_d(aTHX_ packWARN(WARN_EXPERIMENTAL__PRIVATE_USE), "The private_use feature is experimental");
+            }
+        }
+    }
+
+    if (invert_return) {
+        _invlist_invert(prop_definition);
+    }
+    return prop_definition;
+
+
+  failed:
+    if (non_pkg_begin != 0) {
+        if (SvCUR(msg) > 0) sv_catpvs(msg, "; ");
+        sv_catpvs(msg, "Illegal user-defined property name");
+    }
+    else {
+        if (SvCUR(msg) > 0) sv_catpvs(msg, "; ");
+        sv_catpvs(msg, "Can't find Unicode property definition");
+    }
+    /* FALLTHROUGH */
+
+  append_name_to_msg:
+    {
+        const char * prefix = (runtime && level == 0) ?  " \\p{" : " \"";
+        const char * suffix = (runtime && level == 0) ?  "}" : "\"";
+
+        sv_catpv(msg, prefix);
+        Perl_sv_catpvf(aTHX_ msg, "%" UTF8f, UTF8fARG(is_utf8, name_len, name));
+        sv_catpv(msg, suffix);
+    }
+
+    return NULL;
+
+  definition_deferred:
+
+    /* Here it could yet to be defined, so defer evaluation of this
+     * until its needed at runtime.  We need the fully qualified property name
+     * to avoid ambiguity, and a trailing newline */
+    if (! fq_name) {
+        fq_name = S_get_fq_name(aTHX_ name, name_len, is_utf8,
+                                      non_pkg_begin != 0 /* If has "::" */
+                               );
+    }
+    sv_catpvs(fq_name, "\n");
+
+    *user_defined_ptr = TRUE;
+    return fq_name;
 }
 
 #endif