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subsume CURCUR (current curly) struct within the main regmatch_state
[perl5.git] / regexec.c
index b69fd2b..ee8503b 100644 (file)
--- a/regexec.c
+++ b/regexec.c
@@ -5,6 +5,17 @@
  * "One Ring to rule them all, One Ring to find them..."
  */
 
+/* This file contains functions for executing a regular expression.  See
+ * also regcomp.c which funnily enough, contains functions for compiling
+ * a regular expression.
+ *
+ * This file is also copied at build time to ext/re/re_exec.c, where
+ * it's built with -DPERL_EXT_RE_BUILD -DPERL_EXT_RE_DEBUG -DPERL_EXT.
+ * This causes the main functions to be compiled under new names and with
+ * debugging support added, which makes "use re 'debug'" work.
+ */
+
 /* NOTE: this is derived from Henry Spencer's regexp code, and should not
  * confused with the original package (see point 3 below).  Thanks, Henry!
  */
@@ -44,7 +55,6 @@
 #  define PERL_NO_GET_CONTEXT
 #endif
 
-/*SUPPRESS 112*/
 /*
  * pregcomp and pregexec -- regsub and regerror are not used in perl
  *
@@ -67,7 +77,8 @@
  *
  ****    Alterations to Henry's code are...
  ****
- ****    Copyright (c) 1991-2002, Larry Wall
+ ****    Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
+ ****    2000, 2001, 2002, 2003, 2004, 2005, 2006, by Larry Wall and others
  ****
  ****    You may distribute under the terms of either the GNU General Public
  ****    License or the Artistic License, as specified in the README file.
 #define CHR_SVLEN(sv) (do_utf8 ? sv_len_utf8(sv) : SvCUR(sv))
 #define CHR_DIST(a,b) (PL_reg_match_utf8 ? utf8_distance(a,b) : a - b)
 
-#define reghop_c(pos,off) ((char*)reghop((U8*)pos, off))
-#define reghopmaybe_c(pos,off) ((char*)reghopmaybe((U8*)pos, off))
-#define HOP(pos,off) (PL_reg_match_utf8 ? reghop((U8*)pos, off) : (U8*)(pos + off))
-#define HOPMAYBE(pos,off) (PL_reg_match_utf8 ? reghopmaybe((U8*)pos, off) : (U8*)(pos + off))
-#define HOPc(pos,off) ((char*)HOP(pos,off))
-#define HOPMAYBEc(pos,off) ((char*)HOPMAYBE(pos,off))
-
-#define HOPBACK(pos, off) (            \
-    (PL_reg_match_utf8)                        \
-       ? reghopmaybe((U8*)pos, -off)   \
+#define HOPc(pos,off) ((char *)(PL_reg_match_utf8 \
+           ? reghop3((U8*)pos, off, (U8*)(off >= 0 ? PL_regeol : PL_bostr)) \
+           : (U8*)(pos + off)))
+#define HOPBACKc(pos, off) ((char*)    \
+    ((PL_reg_match_utf8)               \
+       ? reghopmaybe3((U8*)pos, -off, ((U8*)(off < 0 ? PL_regeol : PL_bostr))) \
     : (pos - off >= PL_bostr)          \
        ? (U8*)(pos - off)              \
-    : (U8*)NULL                                \
+    : (U8*)NULL)                       \
 )
-#define HOPBACKc(pos, off) (char*)HOPBACK(pos, off)
 
-#define reghop3_c(pos,off,lim) ((char*)reghop3((U8*)pos, off, (U8*)lim))
 #define reghopmaybe3_c(pos,off,lim) ((char*)reghopmaybe3((U8*)pos, off, (U8*)lim))
 #define HOP3(pos,off,lim) (PL_reg_match_utf8 ? reghop3((U8*)pos, off, (U8*)lim) : (U8*)(pos + off))
-#define HOPMAYBE3(pos,off,lim) (PL_reg_match_utf8 ? reghopmaybe3((U8*)pos, off, (U8*)lim) : (U8*)(pos + off))
 #define HOP3c(pos,off,lim) ((char*)HOP3(pos,off,lim))
-#define HOPMAYBE3c(pos,off,lim) ((char*)HOPMAYBE3(pos,off,lim))
 
-#define LOAD_UTF8_CHARCLASS(a,b) STMT_START { if (!CAT2(PL_utf8_,a)) { ENTER; save_re_context(); (void)CAT2(is_utf8_, a)((U8*)b); LEAVE; } } STMT_END
+#define LOAD_UTF8_CHARCLASS(class,str) STMT_START { \
+    if (!CAT2(PL_utf8_,class)) { bool ok; ENTER; save_re_context(); ok=CAT2(is_utf8_,class)((const U8*)str); assert(ok); LEAVE; } } STMT_END
+#define LOAD_UTF8_CHARCLASS_ALNUM() LOAD_UTF8_CHARCLASS(alnum,"a")
+#define LOAD_UTF8_CHARCLASS_DIGIT() LOAD_UTF8_CHARCLASS(digit,"0")
+#define LOAD_UTF8_CHARCLASS_SPACE() LOAD_UTF8_CHARCLASS(space," ")
+#define LOAD_UTF8_CHARCLASS_MARK()  LOAD_UTF8_CHARCLASS(mark, "\xcd\x86")
 
 /* for use after a quantifier and before an EXACT-like node -- japhy */
 #define JUMPABLE(rn) ( \
@@ -162,16 +170,17 @@ static void restore_pos(pTHX_ void *arg);
 STATIC CHECKPOINT
 S_regcppush(pTHX_ I32 parenfloor)
 {
-    int retval = PL_savestack_ix;
+    dVAR;
+    const int retval = PL_savestack_ix;
 #define REGCP_PAREN_ELEMS 4
-    int paren_elems_to_push = (PL_regsize - parenfloor) * REGCP_PAREN_ELEMS;
+    const int paren_elems_to_push = (PL_regsize - parenfloor) * REGCP_PAREN_ELEMS;
     int p;
 
     if (paren_elems_to_push < 0)
        Perl_croak(aTHX_ "panic: paren_elems_to_push < 0");
 
 #define REGCP_OTHER_ELEMS 6
-    SSCHECK(paren_elems_to_push + REGCP_OTHER_ELEMS);
+    SSGROW(paren_elems_to_push + REGCP_OTHER_ELEMS);
     for (p = PL_regsize; p > parenfloor; p--) {
 /* REGCP_PARENS_ELEMS are pushed per pairs of parentheses. */
        SSPUSHINT(PL_regendp[p]);
@@ -194,11 +203,11 @@ S_regcppush(pTHX_ I32 parenfloor)
 }
 
 /* These are needed since we do not localize EVAL nodes: */
-#  define REGCP_SET(cp)  DEBUG_r(PerlIO_printf(Perl_debug_log,         \
+#  define REGCP_SET(cp)  DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log,         \
                             "  Setting an EVAL scope, savestack=%"IVdf"\n",    \
                             (IV)PL_savestack_ix)); cp = PL_savestack_ix
 
-#  define REGCP_UNWIND(cp)  DEBUG_r(cp != PL_savestack_ix ?            \
+#  define REGCP_UNWIND(cp)  DEBUG_EXECUTE_r(cp != PL_savestack_ix ?            \
                                PerlIO_printf(Perl_debug_log,           \
                                "  Clearing an EVAL scope, savestack=%"IVdf"..%"IVdf"\n", \
                                (IV)(cp), (IV)PL_savestack_ix) : 0); regcpblow(cp)
@@ -206,10 +215,12 @@ S_regcppush(pTHX_ I32 parenfloor)
 STATIC char *
 S_regcppop(pTHX)
 {
+    dVAR;
     I32 i;
     U32 paren = 0;
     char *input;
-    I32 tmps;
+
+    GET_RE_DEBUG_FLAGS_DECL;
 
     /* Pop REGCP_OTHER_ELEMS before the parentheses loop starts. */
     i = SSPOPINT;
@@ -223,13 +234,14 @@ S_regcppop(pTHX)
     /* Now restore the parentheses context. */
     for (i -= (REGCP_OTHER_ELEMS - REGCP_FRAME_ELEMS);
         i > 0; i -= REGCP_PAREN_ELEMS) {
+       I32 tmps;
        paren = (U32)SSPOPINT;
        PL_reg_start_tmp[paren] = (char *) SSPOPPTR;
        PL_regstartp[paren] = SSPOPINT;
        tmps = SSPOPINT;
        if (paren <= *PL_reglastparen)
            PL_regendp[paren] = tmps;
-       DEBUG_r(
+       DEBUG_EXECUTE_r(
            PerlIO_printf(Perl_debug_log,
                          "     restoring \\%"UVuf" to %"IVdf"(%"IVdf")..%"IVdf"%s\n",
                          (UV)paren, (IV)PL_regstartp[paren],
@@ -238,7 +250,7 @@ S_regcppop(pTHX)
                          (paren > *PL_reglastparen ? "(no)" : ""));
        );
     }
-    DEBUG_r(
+    DEBUG_EXECUTE_r(
        if ((I32)(*PL_reglastparen + 1) <= PL_regnpar) {
            PerlIO_printf(Perl_debug_log,
                          "     restoring \\%"IVdf"..\\%"IVdf" to undef\n",
@@ -265,29 +277,9 @@ S_regcppop(pTHX)
     return input;
 }
 
-STATIC char *
-S_regcp_set_to(pTHX_ I32 ss)
-{
-    I32 tmp = PL_savestack_ix;
-
-    PL_savestack_ix = ss;
-    regcppop();
-    PL_savestack_ix = tmp;
-    return Nullch;
-}
-
-typedef struct re_cc_state
-{
-    I32 ss;
-    regnode *node;
-    struct re_cc_state *prev;
-    CURCUR *cc;
-    regexp *re;
-} re_cc_state;
-
 #define regcpblow(cp) LEAVE_SCOPE(cp)  /* Ignores regcppush()ed data. */
 
-#define TRYPAREN(paren, n, input) {                            \
+#define TRYPAREN(paren, n, input, where) {                     \
     if (paren) {                                               \
        if (n) {                                                \
            PL_regstartp[paren] = HOPc(input, -1) - PL_bostr;   \
@@ -296,7 +288,8 @@ typedef struct re_cc_state
        else                                                    \
            PL_regendp[paren] = -1;                             \
     }                                                          \
-    if (regmatch(next))                                                \
+    REGMATCH(next, where);                                     \
+    if (result)                                                        \
        sayYES;                                                 \
     if (paren && n)                                            \
        PL_regendp[paren] = -1;                                 \
@@ -326,6 +319,7 @@ Perl_pregexec(pTHX_ register regexp *prog, char *stringarg, register char *stren
 STATIC void
 S_cache_re(pTHX_ regexp *prog)
 {
+    dVAR;
     PL_regprecomp = prog->precomp;             /* Needed for FAIL. */
 #ifdef DEBUGGING
     PL_regprogram = prog->program;
@@ -351,7 +345,7 @@ S_cache_re(pTHX_ regexp *prog)
 
 /* Assumptions: if ANCH_GPOS, then strpos is anchored. XXXX Check GPOS logic */
 
-/* If SCREAM, then SvPVX(sv) should be compatible with strpos and strend.
+/* If SCREAM, then SvPVX_const(sv) should be compatible with strpos and strend.
    Otherwise, only SvCUR(sv) is used to get strbeg. */
 
 /* XXXX We assume that strpos is strbeg unless sv. */
@@ -385,6 +379,7 @@ char *
 Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
                     char *strend, U32 flags, re_scream_pos_data *data)
 {
+    dVAR;
     register I32 start_shift = 0;
     /* Should be nonnegative! */
     register I32 end_shift   = 0;
@@ -392,35 +387,40 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
     register SV *check;
     char *strbeg;
     char *t;
-    int do_utf8 = sv ? SvUTF8(sv) : 0; /* if no sv we have to assume bytes */
+    const int do_utf8 = sv ? SvUTF8(sv) : 0;   /* if no sv we have to assume bytes */
     I32 ml_anch;
-    register char *other_last = Nullch;        /* other substr checked before this */
-    char *check_at = Nullch;           /* check substr found at this pos */
+    register char *other_last = NULL;  /* other substr checked before this */
+    char *check_at = NULL;             /* check substr found at this pos */
+    const I32 multiline = prog->reganch & PMf_MULTILINE;
 #ifdef DEBUGGING
-    char *i_strpos = strpos;
-    SV *dsv = PERL_DEBUG_PAD_ZERO(0);
+    const char * const i_strpos = strpos;
+    SV * const dsv = PERL_DEBUG_PAD_ZERO(0);
 #endif
 
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    RX_MATCH_UTF8_set(prog,do_utf8);
+
     if (prog->reganch & ROPT_UTF8) {
-       DEBUG_r(PerlIO_printf(Perl_debug_log,
+       DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log,
                              "UTF-8 regex...\n"));
        PL_reg_flags |= RF_utf8;
     }
 
-    DEBUG_r({
-        char *s   = PL_reg_match_utf8 ?
+    DEBUG_EXECUTE_r({
+        const char *s   = PL_reg_match_utf8 ?
                         sv_uni_display(dsv, sv, 60, UNI_DISPLAY_REGEX) :
                         strpos;
-        int   len = PL_reg_match_utf8 ?
+        const int   len = PL_reg_match_utf8 ?
                         strlen(s) : strend - strpos;
         if (!PL_colorset)
              reginitcolors();
         if (PL_reg_match_utf8)
-            DEBUG_r(PerlIO_printf(Perl_debug_log,
+            DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log,
                                   "UTF-8 target...\n"));
         PerlIO_printf(Perl_debug_log,
-                      "%sGuessing start of match, REx%s `%s%.60s%s%s' against `%s%.*s%s%s'...\n",
-                      PL_colors[4],PL_colors[5],PL_colors[0],
+                      "%sGuessing start of match, REx%s \"%s%.60s%s%s\" against \"%s%.*s%s%s\"...\n",
+                      PL_colors[4], PL_colors[5], PL_colors[0],
                       prog->precomp,
                       PL_colors[1],
                       (strlen(prog->precomp) > 60 ? "..." : ""),
@@ -433,7 +433,7 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
 
     /* CHR_DIST() would be more correct here but it makes things slow. */
     if (prog->minlen > strend - strpos) {
-       DEBUG_r(PerlIO_printf(Perl_debug_log,
+       DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log,
                              "String too short... [re_intuit_start]\n"));
        goto fail;
     }
@@ -449,22 +449,22 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
        check = prog->check_substr;
     }
    if (check == &PL_sv_undef) {
-       DEBUG_r(PerlIO_printf(Perl_debug_log,
+       DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log,
                "Non-utf string cannot match utf check string\n"));
        goto fail;
     }
     if (prog->reganch & ROPT_ANCH) {   /* Match at beg-of-str or after \n */
        ml_anch = !( (prog->reganch & ROPT_ANCH_SINGLE)
                     || ( (prog->reganch & ROPT_ANCH_BOL)
-                         && !PL_multiline ) ); /* Check after \n? */
+                         && !multiline ) );    /* Check after \n? */
 
        if (!ml_anch) {
          if ( !(prog->reganch & (ROPT_ANCH_GPOS /* Checked by the caller */
                                  | ROPT_IMPLICIT)) /* not a real BOL */
-              /* SvCUR is not set on references: SvRV and SvPVX overlap */
+              /* SvCUR is not set on references: SvRV and SvPVX_const overlap */
               && sv && !SvROK(sv)
               && (strpos != strbeg)) {
-             DEBUG_r(PerlIO_printf(Perl_debug_log, "Not at start...\n"));
+             DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "Not at start...\n"));
              goto fail;
          }
          if (prog->check_offset_min == prog->check_offset_max &&
@@ -478,23 +478,24 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
 
                if ( strend - s > slen || strend - s < slen - 1
                     || (strend - s == slen && strend[-1] != '\n')) {
-                   DEBUG_r(PerlIO_printf(Perl_debug_log, "String too long...\n"));
+                   DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "String too long...\n"));
                    goto fail_finish;
                }
                /* Now should match s[0..slen-2] */
                slen--;
-               if (slen && (*SvPVX(check) != *s
+               if (slen && (*SvPVX_const(check) != *s
                             || (slen > 1
-                                && memNE(SvPVX(check), s, slen)))) {
+                                && memNE(SvPVX_const(check), s, slen)))) {
                  report_neq:
-                   DEBUG_r(PerlIO_printf(Perl_debug_log, "String not equal...\n"));
+                   DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "String not equal...\n"));
                    goto fail_finish;
                }
            }
-           else if (*SvPVX(check) != *s
+           else if (*SvPVX_const(check) != *s
                     || ((slen = SvCUR(check)) > 1
-                        && memNE(SvPVX(check), s, slen)))
+                        && memNE(SvPVX_const(check), s, slen)))
                goto report_neq;
+           check_at = s;
            goto success_at_start;
          }
        }
@@ -504,9 +505,9 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
        end_shift = prog->minlen - start_shift -
            CHR_SVLEN(check) + (SvTAIL(check) != 0);
        if (!ml_anch) {
-           I32 end = prog->check_offset_max + CHR_SVLEN(check)
+           const I32 end = prog->check_offset_max + CHR_SVLEN(check)
                                         - (SvTAIL(check) != 0);
-           I32 eshift = CHR_DIST((U8*)strend, (U8*)s) - end;
+           const I32 eshift = CHR_DIST((U8*)strend, (U8*)s) - end;
 
            if (end_shift < eshift)
                end_shift = eshift;
@@ -531,7 +532,7 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
        the "check" substring in the region corrected by start/end_shift. */
     if (flags & REXEC_SCREAM) {
        I32 p = -1;                     /* Internal iterator of scream. */
-       I32 *pp = data ? data->scream_pos : &p;
+       I32 * const pp = data ? data->scream_pos : &p;
 
        if (PL_screamfirst[BmRARE(check)] >= 0
            || ( BmRARE(check) == '\n'
@@ -541,27 +542,30 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
                            start_shift + (s - strbeg), end_shift, pp, 0);
        else
            goto fail_finish;
+       /* we may be pointing at the wrong string */
+       if (s && RX_MATCH_COPIED(prog))
+           s = strbeg + (s - SvPVX_const(sv));
        if (data)
            *data->scream_olds = s;
     }
     else if (prog->reganch & ROPT_CANY_SEEN)
        s = fbm_instr((U8*)(s + start_shift),
                      (U8*)(strend - end_shift),
-                     check, PL_multiline ? FBMrf_MULTILINE : 0);
+                     check, multiline ? FBMrf_MULTILINE : 0);
     else
        s = fbm_instr(HOP3(s, start_shift, strend),
                      HOP3(strend, -end_shift, strbeg),
-                     check, PL_multiline ? FBMrf_MULTILINE : 0);
+                     check, multiline ? FBMrf_MULTILINE : 0);
 
     /* Update the count-of-usability, remove useless subpatterns,
        unshift s.  */
 
-    DEBUG_r(PerlIO_printf(Perl_debug_log, "%s %s substr `%s%.*s%s'%s%s",
+    DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "%s %s substr \"%s%.*s%s\"%s%s",
                          (s ? "Found" : "Did not find"),
                          (check == (do_utf8 ? prog->anchored_utf8 : prog->anchored_substr) ? "anchored" : "floating"),
                          PL_colors[0],
                          (int)(SvCUR(check) - (SvTAIL(check)!=0)),
-                         SvPVX(check),
+                         SvPVX_const(check),
                          PL_colors[1], (SvTAIL(check) ? "$" : ""),
                          (s ? " at offset " : "...\n") ) );
 
@@ -571,12 +575,12 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
     check_at = s;
 
     /* Finish the diagnostic message */
-    DEBUG_r(PerlIO_printf(Perl_debug_log, "%ld...\n", (long)(s - i_strpos)) );
+    DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "%ld...\n", (long)(s - i_strpos)) );
 
     /* Got a candidate.  Check MBOL anchoring, and the *other* substr.
        Start with the other substr.
        XXXX no SCREAM optimization yet - and a very coarse implementation
-       XXXX /ttx+/ results in anchored=`ttx', floating=`x'.  floating will
+       XXXX /ttx+/ results in anchored="ttx", floating="x".  floating will
                *always* match.  Probably should be marked during compile...
        Probably it is right to do no SCREAM here...
      */
@@ -589,13 +593,14 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
        if (check == (do_utf8 ? prog->float_utf8 : prog->float_substr)) {
          do_other_anchored:
            {
-               char *last = HOP3c(s, -start_shift, strbeg), *last1, *last2;
+               char * const last = HOP3c(s, -start_shift, strbeg);
+               char *last1, *last2;
                char *s1 = s;
                SV* must;
 
                t = s - prog->check_offset_max;
                if (s - strpos > prog->check_offset_max  /* signed-corrected t > strpos */
-                   && (!(prog->reganch & ROPT_UTF8)
+                   && (!do_utf8
                        || ((t = reghopmaybe3_c(s, -(prog->check_offset_max), strpos))
                            && t > strpos)))
                    /* EMPTY */;
@@ -612,7 +617,7 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
                must = do_utf8 ? prog->anchored_utf8 : prog->anchored_substr;
                if (must == &PL_sv_undef) {
                    s = (char*)NULL;
-                   DEBUG_r(must = prog->anchored_utf8);        /* for debug */
+                   DEBUG_EXECUTE_r(must = prog->anchored_utf8);        /* for debug */
                }
                else
                    s = fbm_instr(
@@ -620,23 +625,23 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
                        HOP3(HOP3(last1, prog->anchored_offset, strend)
                                + SvCUR(must), -(SvTAIL(must)!=0), strbeg),
                        must,
-                       PL_multiline ? FBMrf_MULTILINE : 0
+                       multiline ? FBMrf_MULTILINE : 0
                    );
-               DEBUG_r(PerlIO_printf(Perl_debug_log,
-                       "%s anchored substr `%s%.*s%s'%s",
+               DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log,
+                       "%s anchored substr \"%s%.*s%s\"%s",
                        (s ? "Found" : "Contradicts"),
                        PL_colors[0],
                          (int)(SvCUR(must)
                          - (SvTAIL(must)!=0)),
-                         SvPVX(must),
+                         SvPVX_const(must),
                          PL_colors[1], (SvTAIL(must) ? "$" : "")));
                if (!s) {
                    if (last1 >= last2) {
-                       DEBUG_r(PerlIO_printf(Perl_debug_log,
+                       DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log,
                                                ", giving up...\n"));
                        goto fail_finish;
                    }
-                   DEBUG_r(PerlIO_printf(Perl_debug_log,
+                   DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log,
                        ", trying floating at offset %ld...\n",
                        (long)(HOP3c(s1, 1, strend) - i_strpos)));
                    other_last = HOP3c(last1, prog->anchored_offset+1, strend);
@@ -644,7 +649,7 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
                    goto restart;
                }
                else {
-                   DEBUG_r(PerlIO_printf(Perl_debug_log, " at offset %ld...\n",
+                   DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, " at offset %ld...\n",
                          (long)(s - i_strpos)));
                    t = HOP3c(s, -prog->anchored_offset, strbeg);
                    other_last = HOP3c(s, 1, strend);
@@ -675,26 +680,26 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
               and end-of-str is not later than strend we are OK. */
            if (must == &PL_sv_undef) {
                s = (char*)NULL;
-               DEBUG_r(must = prog->float_utf8);       /* for debug message */
+               DEBUG_EXECUTE_r(must = prog->float_utf8);       /* for debug message */
            }
            else
                s = fbm_instr((unsigned char*)s,
                              (unsigned char*)last + SvCUR(must)
                                  - (SvTAIL(must)!=0),
-                             must, PL_multiline ? FBMrf_MULTILINE : 0);
-           DEBUG_r(PerlIO_printf(Perl_debug_log, "%s floating substr `%s%.*s%s'%s",
+                             must, multiline ? FBMrf_MULTILINE : 0);
+           DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "%s floating substr \"%s%.*s%s\"%s",
                    (s ? "Found" : "Contradicts"),
                    PL_colors[0],
                      (int)(SvCUR(must) - (SvTAIL(must)!=0)),
-                     SvPVX(must),
+                     SvPVX_const(must),
                      PL_colors[1], (SvTAIL(must) ? "$" : "")));
            if (!s) {
                if (last1 == last) {
-                   DEBUG_r(PerlIO_printf(Perl_debug_log,
+                   DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log,
                                            ", giving up...\n"));
                    goto fail_finish;
                }
-               DEBUG_r(PerlIO_printf(Perl_debug_log,
+               DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log,
                    ", trying anchored starting at offset %ld...\n",
                    (long)(s1 + 1 - i_strpos)));
                other_last = last;
@@ -702,7 +707,7 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
                goto restart;
            }
            else {
-               DEBUG_r(PerlIO_printf(Perl_debug_log, " at offset %ld...\n",
+               DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, " at offset %ld...\n",
                      (long)(s - i_strpos)));
                other_last = s; /* Fix this later. --Hugo */
                s = s1;
@@ -715,7 +720,7 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
 
     t = s - prog->check_offset_max;
     if (s - strpos > prog->check_offset_max  /* signed-corrected t > strpos */
-        && (!(prog->reganch & ROPT_UTF8)
+        && (!do_utf8
            || ((t = reghopmaybe3_c(s, -prog->check_offset_max, strpos))
                 && t > strpos))) {
        /* Fixed substring is found far enough so that the match
@@ -741,34 +746,34 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
                               is float.  Redo checking for "other"=="fixed".
                             */
                            strpos = t + 1;                     
-                           DEBUG_r(PerlIO_printf(Perl_debug_log, "Found /%s^%s/m at offset %ld, rescanning for anchored from offset %ld...\n",
-                               PL_colors[0],PL_colors[1], (long)(strpos - i_strpos), (long)(strpos - i_strpos + prog->anchored_offset)));
+                           DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "Found /%s^%s/m at offset %ld, rescanning for anchored from offset %ld...\n",
+                               PL_colors[0], PL_colors[1], (long)(strpos - i_strpos), (long)(strpos - i_strpos + prog->anchored_offset)));
                            goto do_other_anchored;
                        }
                        /* We don't contradict the found floating substring. */
                        /* XXXX Why not check for STCLASS? */
                        s = t + 1;
-                       DEBUG_r(PerlIO_printf(Perl_debug_log, "Found /%s^%s/m at offset %ld...\n",
-                           PL_colors[0],PL_colors[1], (long)(s - i_strpos)));
+                       DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "Found /%s^%s/m at offset %ld...\n",
+                           PL_colors[0], PL_colors[1], (long)(s - i_strpos)));
                        goto set_useful;
                    }
                    /* Position contradicts check-string */
                    /* XXXX probably better to look for check-string
                       than for "\n", so one should lower the limit for t? */
-                   DEBUG_r(PerlIO_printf(Perl_debug_log, "Found /%s^%s/m, restarting lookup for check-string at offset %ld...\n",
-                       PL_colors[0],PL_colors[1], (long)(t + 1 - i_strpos)));
+                   DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "Found /%s^%s/m, restarting lookup for check-string at offset %ld...\n",
+                       PL_colors[0], PL_colors[1], (long)(t + 1 - i_strpos)));
                    other_last = strpos = s = t + 1;
                    goto restart;
                }
                t++;
            }
-           DEBUG_r(PerlIO_printf(Perl_debug_log, "Did not find /%s^%s/m...\n",
-                       PL_colors[0],PL_colors[1]));
+           DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "Did not find /%s^%s/m...\n",
+                       PL_colors[0], PL_colors[1]));
            goto fail_finish;
        }
        else {
-           DEBUG_r(PerlIO_printf(Perl_debug_log, "Starting position does not contradict /%s^%s/m...\n",
-                       PL_colors[0],PL_colors[1]));
+           DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "Starting position does not contradict /%s^%s/m...\n",
+                       PL_colors[0], PL_colors[1]));
        }
        s = t;
       set_useful:
@@ -790,9 +795,9 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
            t = strpos;
            goto find_anchor;
        }
-       DEBUG_r( if (ml_anch)
+       DEBUG_EXECUTE_r( if (ml_anch)
            PerlIO_printf(Perl_debug_log, "Position at offset %ld does not contradict /%s^%s/m...\n",
-                       (long)(strpos - i_strpos), PL_colors[0],PL_colors[1]);
+                       (long)(strpos - i_strpos), PL_colors[0], PL_colors[1]);
        );
       success_at_start:
        if (!(prog->reganch & ROPT_NAUGHTY)     /* XXXX If strpos moved? */
@@ -807,13 +812,13 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
            )))
        {
            /* If flags & SOMETHING - do not do it many times on the same match */
-           DEBUG_r(PerlIO_printf(Perl_debug_log, "... Disabling check substring...\n"));
+           DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "... Disabling check substring...\n"));
            SvREFCNT_dec(do_utf8 ? prog->check_utf8 : prog->check_substr);
            if (do_utf8 ? prog->check_substr : prog->check_utf8)
                SvREFCNT_dec(do_utf8 ? prog->check_substr : prog->check_utf8);
-           prog->check_substr = prog->check_utf8 = Nullsv;     /* disable */
-           prog->float_substr = prog->float_utf8 = Nullsv;     /* clear */
-           check = Nullsv;                     /* abort */
+           prog->check_substr = prog->check_utf8 = NULL;       /* disable */
+           prog->float_substr = prog->float_utf8 = NULL;       /* clear */
+           check = NULL;                       /* abort */
            s = strpos;
            /* XXXX This is a remnant of the old implementation.  It
                    looks wasteful, since now INTUIT can use many
@@ -835,52 +840,48 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
           regstclass does not come from lookahead...  */
        /* If regstclass takes bytelength more than 1: If charlength==1, OK.
           This leaves EXACTF only, which is dealt with in find_byclass().  */
-       U8* str = (U8*)STRING(prog->regstclass);
-       int cl_l = (PL_regkind[(U8)OP(prog->regstclass)] == EXACT
+        const U8* const str = (U8*)STRING(prog->regstclass);
+        const int cl_l = (PL_regkind[(U8)OP(prog->regstclass)] == EXACT
                    ? CHR_DIST(str+STR_LEN(prog->regstclass), str)
                    : 1);
-       char *endpos = (prog->anchored_substr || prog->anchored_utf8 || ml_anch)
+       const char * const endpos = (prog->anchored_substr || prog->anchored_utf8 || ml_anch)
                ? HOP3c(s, (prog->minlen ? cl_l : 0), strend)
                : (prog->float_substr || prog->float_utf8
                   ? HOP3c(HOP3c(check_at, -start_shift, strbeg),
                           cl_l, strend)
                   : strend);
-       char *startpos = strbeg;
 
        t = s;
-       if (prog->reganch & ROPT_UTF8) {        
-           PL_regdata = prog->data;
-           PL_bostr = startpos;
-       }
-       s = find_byclass(prog, prog->regstclass, s, endpos, startpos, 1);
+       cache_re(prog);
+        s = find_byclass(prog, prog->regstclass, s, endpos, 1);
        if (!s) {
 #ifdef DEBUGGING
-           char *what = 0;
+           const char *what = NULL;
 #endif
            if (endpos == strend) {
-               DEBUG_r( PerlIO_printf(Perl_debug_log,
+               DEBUG_EXECUTE_r( PerlIO_printf(Perl_debug_log,
                                "Could not match STCLASS...\n") );
                goto fail;
            }
-           DEBUG_r( PerlIO_printf(Perl_debug_log,
+           DEBUG_EXECUTE_r( PerlIO_printf(Perl_debug_log,
                                   "This position contradicts STCLASS...\n") );
            if ((prog->reganch & ROPT_ANCH) && !ml_anch)
                goto fail;
            /* Contradict one of substrings */
            if (prog->anchored_substr || prog->anchored_utf8) {
                if ((do_utf8 ? prog->anchored_utf8 : prog->anchored_substr) == check) {
-                   DEBUG_r( what = "anchored" );
+                   DEBUG_EXECUTE_r( what = "anchored" );
                  hop_and_restart:
                    s = HOP3c(t, 1, strend);
                    if (s + start_shift + end_shift > strend) {
                        /* XXXX Should be taken into account earlier? */
-                       DEBUG_r( PerlIO_printf(Perl_debug_log,
+                       DEBUG_EXECUTE_r( PerlIO_printf(Perl_debug_log,
                                               "Could not match STCLASS...\n") );
                        goto fail;
                    }
                    if (!check)
                        goto giveup;
-                   DEBUG_r( PerlIO_printf(Perl_debug_log,
+                   DEBUG_EXECUTE_r( PerlIO_printf(Perl_debug_log,
                                "Looking for %s substr starting at offset %ld...\n",
                                 what, (long)(s + start_shift - i_strpos)) );
                    goto restart;
@@ -892,7 +893,7 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
                s = check_at;
                if (!check)
                    goto giveup;
-               DEBUG_r( PerlIO_printf(Perl_debug_log,
+               DEBUG_EXECUTE_r( PerlIO_printf(Perl_debug_log,
                          "Looking for anchored substr starting at offset %ld...\n",
                          (long)(other_last - i_strpos)) );
                goto do_other_anchored;
@@ -903,9 +904,9 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
                s = t = t + 1;
                if (!check)
                    goto giveup;
-               DEBUG_r( PerlIO_printf(Perl_debug_log,
+               DEBUG_EXECUTE_r( PerlIO_printf(Perl_debug_log,
                          "Looking for /%s^%s/m starting at offset %ld...\n",
-                         PL_colors[0],PL_colors[1], (long)(t - i_strpos)) );
+                         PL_colors[0], PL_colors[1], (long)(t - i_strpos)) );
                goto try_at_offset;
            }
            if (!(do_utf8 ? prog->float_utf8 : prog->float_substr))     /* Could have been deleted */
@@ -913,23 +914,23 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
            /* Check is floating subtring. */
          retry_floating_check:
            t = check_at - start_shift;
-           DEBUG_r( what = "floating" );
+           DEBUG_EXECUTE_r( what = "floating" );
            goto hop_and_restart;
        }
        if (t != s) {
-            DEBUG_r(PerlIO_printf(Perl_debug_log,
+            DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log,
                        "By STCLASS: moving %ld --> %ld\n",
                                   (long)(t - i_strpos), (long)(s - i_strpos))
                    );
         }
         else {
-            DEBUG_r(PerlIO_printf(Perl_debug_log,
+            DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log,
                                   "Does not contradict STCLASS...\n"); 
                    );
         }
     }
   giveup:
-    DEBUG_r(PerlIO_printf(Perl_debug_log, "%s%s:%s match at offset %ld\n",
+    DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "%s%s:%s match at offset %ld\n",
                          PL_colors[4], (check ? "Guessed" : "Giving up"),
                          PL_colors[5], (long)(s - i_strpos)) );
     return s;
@@ -938,46 +939,64 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
     if (prog->check_substr || prog->check_utf8)                /* could be removed already */
        BmUSEFUL(do_utf8 ? prog->check_utf8 : prog->check_substr) += 5; /* hooray */
   fail:
-    DEBUG_r(PerlIO_printf(Perl_debug_log, "%sMatch rejected by optimizer%s\n",
-                         PL_colors[4],PL_colors[5]));
-    return Nullch;
+    DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "%sMatch rejected by optimizer%s\n",
+                         PL_colors[4], PL_colors[5]));
+    return NULL;
 }
 
 /* We know what class REx starts with.  Try to find this position... */
 STATIC char *
-S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *startpos, I32 norun)
+S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32 norun)
 {
-       I32 doevery = (prog->reganch & ROPT_SKIP) == 0;
+       dVAR;
+       const I32 doevery = (prog->reganch & ROPT_SKIP) == 0;
        char *m;
        STRLEN ln;
+       STRLEN lnc;
+       register STRLEN uskip;
        unsigned int c1;
        unsigned int c2;
        char *e;
        register I32 tmp = 1;   /* Scratch variable? */
-       register bool do_utf8 = PL_reg_match_utf8;
+       register const bool do_utf8 = PL_reg_match_utf8;
 
        /* We know what class it must start with. */
        switch (OP(c)) {
        case ANYOF:
-           while (s < strend) {
-               STRLEN skip = do_utf8 ? UTF8SKIP(s) : 1;
-                 
-               if (do_utf8 ?
-                   reginclass(c, (U8*)s, 0, do_utf8) :
-                   REGINCLASS(c, (U8*)s) ||
-                   (ANYOF_FOLD_SHARP_S(c, s, strend) &&
-                    /* The assignment of 2 is intentional:
-                     * for the sharp s, the skip is 2. */
-                    (skip = SHARP_S_SKIP)
-                    )) {
-                   if (tmp && (norun || regtry(prog, s)))
-                       goto got_it;
-                   else
-                       tmp = doevery;
-               }
-               else 
-                   tmp = 1;
-               s += skip;
+           if (do_utf8) {
+                while (s + (uskip = UTF8SKIP(s)) <= strend) {
+                     if ((ANYOF_FLAGS(c) & ANYOF_UNICODE) ||
+                         !UTF8_IS_INVARIANT((U8)s[0]) ?
+                         reginclass(c, (U8*)s, 0, do_utf8) :
+                         REGINCLASS(c, (U8*)s)) {
+                          if (tmp && (norun || regtry(prog, s)))
+                               goto got_it;
+                          else
+                               tmp = doevery;
+                     }
+                     else 
+                          tmp = 1;
+                     s += uskip;
+                }
+           }
+           else {
+                while (s < strend) {
+                     STRLEN skip = 1;
+
+                     if (REGINCLASS(c, (U8*)s) ||
+                         (ANYOF_FOLD_SHARP_S(c, s, strend) &&
+                          /* The assignment of 2 is intentional:
+                           * for the folded sharp s, the skip is 2. */
+                          (skip = SHARP_S_SKIP))) {
+                          if (tmp && (norun || regtry(prog, s)))
+                               goto got_it;
+                          else
+                               tmp = doevery;
+                     }
+                     else 
+                          tmp = 1;
+                     s += skip;
+                }
            }
            break;
        case CANY:
@@ -990,20 +1009,28 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
            }
            break;
        case EXACTF:
-           m = STRING(c);
-           ln = STR_LEN(c);
+           m   = STRING(c);
+           ln  = STR_LEN(c);   /* length to match in octets/bytes */
+           lnc = (I32) ln;     /* length to match in characters */
            if (UTF) {
                STRLEN ulen1, ulen2;
-               U8 tmpbuf1[UTF8_MAXLEN_UCLC+1];
-               U8 tmpbuf2[UTF8_MAXLEN_UCLC+1];
+               U8 *sm = (U8 *) m;
+               U8 tmpbuf1[UTF8_MAXBYTES_CASE+1];
+               U8 tmpbuf2[UTF8_MAXBYTES_CASE+1];
+               const U32 uniflags = ckWARN(WARN_UTF8) ? 0 : UTF8_ALLOW_ANY;
 
                to_utf8_lower((U8*)m, tmpbuf1, &ulen1);
                to_utf8_upper((U8*)m, tmpbuf2, &ulen2);
 
-               c1 = utf8n_to_uvchr(tmpbuf1, UTF8_MAXLEN_UCLC, 
-                                   0, ckWARN(WARN_UTF8) ? 0 : UTF8_ALLOW_ANY);
-               c2 = utf8n_to_uvchr(tmpbuf2, UTF8_MAXLEN_UCLC,
-                                   0, ckWARN(WARN_UTF8) ? 0 : UTF8_ALLOW_ANY);
+               c1 = utf8n_to_uvchr(tmpbuf1, UTF8_MAXBYTES_CASE, 
+                                   0, uniflags);
+               c2 = utf8n_to_uvchr(tmpbuf2, UTF8_MAXBYTES_CASE,
+                                   0, uniflags);
+               lnc = 0;
+               while (sm < ((U8 *) m + ln)) {
+                   lnc++;
+                   sm += UTF8SKIP(sm);
+               }
            }
            else {
                c1 = *(U8*)m;
@@ -1011,12 +1038,13 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
            }
            goto do_exactf;
        case EXACTFL:
-           m = STRING(c);
-           ln = STR_LEN(c);
+           m   = STRING(c);
+           ln  = STR_LEN(c);
+           lnc = (I32) ln;
            c1 = *(U8*)m;
            c2 = PL_fold_locale[c1];
          do_exactf:
-           e = HOP3c(strend, -(I32)ln, s);
+           e = HOP3c(strend, -((I32)lnc), s);
 
            if (norun && e < s)
                e = s;                  /* Due to minlen logic of intuit() */
@@ -1034,15 +1062,15 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
 
            if (do_utf8) {
                UV c, f;
-               U8 tmpbuf [UTF8_MAXLEN+1];
-               U8 foldbuf[UTF8_MAXLEN_FOLD+1];
+               U8 tmpbuf [UTF8_MAXBYTES+1];
                STRLEN len, foldlen;
-               
+               const U32 uniflags = ckWARN(WARN_UTF8) ? 0 : UTF8_ALLOW_ANY;
                if (c1 == c2) {
+                   /* Upper and lower of 1st char are equal -
+                    * probably not a "letter". */
                    while (s <= e) {
-                       c = utf8n_to_uvchr((U8*)s, UTF8_MAXLEN, &len,
-                                          ckWARN(WARN_UTF8) ?
-                                          0 : UTF8_ALLOW_ANY);
+                       c = utf8n_to_uvchr((U8*)s, UTF8_MAXBYTES, &len,
+                                          uniflags);
                        if ( c == c1
                             && (ln == len ||
                                 ibcmp_utf8(s, (char **)0, 0,  do_utf8,
@@ -1050,6 +1078,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
                             && (norun || regtry(prog, s)) )
                            goto got_it;
                        else {
+                            U8 foldbuf[UTF8_MAXBYTES_CASE+1];
                             uvchr_to_utf8(tmpbuf, c);
                             f = to_utf8_fold(tmpbuf, foldbuf, &foldlen);
                             if ( f != c
@@ -1067,9 +1096,8 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
                }
                else {
                    while (s <= e) {
-                     c = utf8n_to_uvchr((U8*)s, UTF8_MAXLEN, &len,
-                                          ckWARN(WARN_UTF8) ?
-                                          0 : UTF8_ALLOW_ANY);
+                     c = utf8n_to_uvchr((U8*)s, UTF8_MAXBYTES, &len,
+                                          uniflags);
 
                        /* Handle some of the three Greek sigmas cases.
                         * Note that not all the possible combinations
@@ -1089,6 +1117,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
                             && (norun || regtry(prog, s)) )
                            goto got_it;
                        else {
+                            U8 foldbuf[UTF8_MAXBYTES_CASE+1];
                             uvchr_to_utf8(tmpbuf, c);
                             f = to_utf8_fold(tmpbuf, foldbuf, &foldlen);
                             if ( f != c
@@ -1136,14 +1165,13 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
                if (s == PL_bostr)
                    tmp = '\n';
                else {
-                   U8 *r = reghop3((U8*)s, -1, (U8*)PL_bostr);
-               
+                   U8 * const r = reghop3((U8*)s, -1, (U8*)PL_bostr);
                    tmp = utf8n_to_uvchr(r, UTF8SKIP(r), 0, 0);
                }
                tmp = ((OP(c) == BOUND ?
                        isALNUM_uni(tmp) : isALNUM_LC_uvchr(UNI_TO_NATIVE(tmp))) != 0);
-               LOAD_UTF8_CHARCLASS(alnum,"a");
-               while (s < strend) {
+               LOAD_UTF8_CHARCLASS_ALNUM();
+               while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (tmp == !(OP(c) == BOUND ?
                                 swash_fetch(PL_utf8_alnum, (U8*)s, do_utf8) :
                                 isALNUM_LC_utf8((U8*)s)))
@@ -1152,7 +1180,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
                        if ((norun || regtry(prog, s)))
                            goto got_it;
                    }
-                   s += UTF8SKIP(s);
+                   s += uskip;
                }
            }
            else {
@@ -1179,21 +1207,20 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
                if (s == PL_bostr)
                    tmp = '\n';
                else {
-                   U8 *r = reghop3((U8*)s, -1, (U8*)PL_bostr);
-               
+                   U8 * const r = reghop3((U8*)s, -1, (U8*)PL_bostr);
                    tmp = utf8n_to_uvchr(r, UTF8SKIP(r), 0, 0);
                }
                tmp = ((OP(c) == NBOUND ?
                        isALNUM_uni(tmp) : isALNUM_LC_uvchr(UNI_TO_NATIVE(tmp))) != 0);
-               LOAD_UTF8_CHARCLASS(alnum,"a");
-               while (s < strend) {
+               LOAD_UTF8_CHARCLASS_ALNUM();
+               while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (tmp == !(OP(c) == NBOUND ?
                                 swash_fetch(PL_utf8_alnum, (U8*)s, do_utf8) :
                                 isALNUM_LC_utf8((U8*)s)))
                        tmp = !tmp;
                    else if ((norun || regtry(prog, s)))
                        goto got_it;
-                   s += UTF8SKIP(s);
+                   s += uskip;
                }
            }
            else {
@@ -1214,8 +1241,8 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
            break;
        case ALNUM:
            if (do_utf8) {
-               LOAD_UTF8_CHARCLASS(alnum,"a");
-               while (s < strend) {
+               LOAD_UTF8_CHARCLASS_ALNUM();
+               while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (swash_fetch(PL_utf8_alnum, (U8*)s, do_utf8)) {
                        if (tmp && (norun || regtry(prog, s)))
                            goto got_it;
@@ -1224,7 +1251,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
                    }
                    else
                        tmp = 1;
-                   s += UTF8SKIP(s);
+                   s += uskip;
                }
            }
            else {
@@ -1244,7 +1271,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
        case ALNUML:
            PL_reg_flags |= RF_tainted;
            if (do_utf8) {
-               while (s < strend) {
+               while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (isALNUM_LC_utf8((U8*)s)) {
                        if (tmp && (norun || regtry(prog, s)))
                            goto got_it;
@@ -1253,7 +1280,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
                    }
                    else
                        tmp = 1;
-                   s += UTF8SKIP(s);
+                   s += uskip;
                }
            }
            else {
@@ -1272,8 +1299,8 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
            break;
        case NALNUM:
            if (do_utf8) {
-               LOAD_UTF8_CHARCLASS(alnum,"a");
-               while (s < strend) {
+               LOAD_UTF8_CHARCLASS_ALNUM();
+               while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (!swash_fetch(PL_utf8_alnum, (U8*)s, do_utf8)) {
                        if (tmp && (norun || regtry(prog, s)))
                            goto got_it;
@@ -1282,7 +1309,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
                    }
                    else
                        tmp = 1;
-                   s += UTF8SKIP(s);
+                   s += uskip;
                }
            }
            else {
@@ -1302,7 +1329,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
        case NALNUML:
            PL_reg_flags |= RF_tainted;
            if (do_utf8) {
-               while (s < strend) {
+               while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (!isALNUM_LC_utf8((U8*)s)) {
                        if (tmp && (norun || regtry(prog, s)))
                            goto got_it;
@@ -1311,7 +1338,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
                    }
                    else
                        tmp = 1;
-                   s += UTF8SKIP(s);
+                   s += uskip;
                }
            }
            else {
@@ -1330,8 +1357,8 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
            break;
        case SPACE:
            if (do_utf8) {
-               LOAD_UTF8_CHARCLASS(space," ");
-               while (s < strend) {
+               LOAD_UTF8_CHARCLASS_SPACE();
+               while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (*s == ' ' || swash_fetch(PL_utf8_space,(U8*)s, do_utf8)) {
                        if (tmp && (norun || regtry(prog, s)))
                            goto got_it;
@@ -1340,7 +1367,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
                    }
                    else
                        tmp = 1;
-                   s += UTF8SKIP(s);
+                   s += uskip;
                }
            }
            else {
@@ -1360,7 +1387,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
        case SPACEL:
            PL_reg_flags |= RF_tainted;
            if (do_utf8) {
-               while (s < strend) {
+               while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (*s == ' ' || isSPACE_LC_utf8((U8*)s)) {
                        if (tmp && (norun || regtry(prog, s)))
                            goto got_it;
@@ -1369,7 +1396,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
                    }
                    else
                        tmp = 1;
-                   s += UTF8SKIP(s);
+                   s += uskip;
                }
            }
            else {
@@ -1388,8 +1415,8 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
            break;
        case NSPACE:
            if (do_utf8) {
-               LOAD_UTF8_CHARCLASS(space," ");
-               while (s < strend) {
+               LOAD_UTF8_CHARCLASS_SPACE();
+               while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (!(*s == ' ' || swash_fetch(PL_utf8_space,(U8*)s, do_utf8))) {
                        if (tmp && (norun || regtry(prog, s)))
                            goto got_it;
@@ -1398,7 +1425,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
                    }
                    else
                        tmp = 1;
-                   s += UTF8SKIP(s);
+                   s += uskip;
                }
            }
            else {
@@ -1418,7 +1445,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
        case NSPACEL:
            PL_reg_flags |= RF_tainted;
            if (do_utf8) {
-               while (s < strend) {
+               while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (!(*s == ' ' || isSPACE_LC_utf8((U8*)s))) {
                        if (tmp && (norun || regtry(prog, s)))
                            goto got_it;
@@ -1427,7 +1454,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
                    }
                    else
                        tmp = 1;
-                   s += UTF8SKIP(s);
+                   s += uskip;
                }
            }
            else {
@@ -1446,8 +1473,8 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
            break;
        case DIGIT:
            if (do_utf8) {
-               LOAD_UTF8_CHARCLASS(digit,"0");
-               while (s < strend) {
+               LOAD_UTF8_CHARCLASS_DIGIT();
+               while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (swash_fetch(PL_utf8_digit,(U8*)s, do_utf8)) {
                        if (tmp && (norun || regtry(prog, s)))
                            goto got_it;
@@ -1456,7 +1483,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
                    }
                    else
                        tmp = 1;
-                   s += UTF8SKIP(s);
+                   s += uskip;
                }
            }
            else {
@@ -1476,7 +1503,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
        case DIGITL:
            PL_reg_flags |= RF_tainted;
            if (do_utf8) {
-               while (s < strend) {
+               while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (isDIGIT_LC_utf8((U8*)s)) {
                        if (tmp && (norun || regtry(prog, s)))
                            goto got_it;
@@ -1485,7 +1512,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
                    }
                    else
                        tmp = 1;
-                   s += UTF8SKIP(s);
+                   s += uskip;
                }
            }
            else {
@@ -1504,8 +1531,8 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
            break;
        case NDIGIT:
            if (do_utf8) {
-               LOAD_UTF8_CHARCLASS(digit,"0");
-               while (s < strend) {
+               LOAD_UTF8_CHARCLASS_DIGIT();
+               while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (!swash_fetch(PL_utf8_digit,(U8*)s, do_utf8)) {
                        if (tmp && (norun || regtry(prog, s)))
                            goto got_it;
@@ -1514,7 +1541,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
                    }
                    else
                        tmp = 1;
-                   s += UTF8SKIP(s);
+                   s += uskip;
                }
            }
            else {
@@ -1534,7 +1561,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
        case NDIGITL:
            PL_reg_flags |= RF_tainted;
            if (do_utf8) {
-               while (s < strend) {
+               while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (!isDIGIT_LC_utf8((U8*)s)) {
                        if (tmp && (norun || regtry(prog, s)))
                            goto got_it;
@@ -1543,7 +1570,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, char *strend, char *sta
                    }
                    else
                        tmp = 1;
-                   s += UTF8SKIP(s);
+                   s += uskip;
                }
            }
            else {
@@ -1581,24 +1608,27 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
 /* data: May be used for some additional optimizations. */
 /* nosave: For optimizations. */
 {
+    dVAR;
     register char *s;
     register regnode *c;
     register char *startpos = stringarg;
     I32 minlen;                /* must match at least this many chars */
     I32 dontbother = 0;        /* how many characters not to try at end */
-    /* I32 start_shift = 0; */         /* Offset of the start to find
-                                        constant substr. */            /* CC */
     I32 end_shift = 0;                 /* Same for the end. */         /* CC */
     I32 scream_pos = -1;               /* Internal iterator of scream. */
-    char *scream_olds;
+    char *scream_olds = NULL;
     SV* oreplsv = GvSV(PL_replgv);
-    bool do_utf8 = DO_UTF8(sv);
+    const bool do_utf8 = DO_UTF8(sv);
+    const I32 multiline = prog->reganch & PMf_MULTILINE;
 #ifdef DEBUGGING
-    SV *dsv0 = PERL_DEBUG_PAD_ZERO(0);
-    SV *dsv1 = PERL_DEBUG_PAD_ZERO(1);
+    SV * const dsv0 = PERL_DEBUG_PAD_ZERO(0);
+    SV * const dsv1 = PERL_DEBUG_PAD_ZERO(1);
 #endif
 
-    PL_regcc = 0;
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_UNUSED_ARG(data);
+    RX_MATCH_UTF8_set(prog,do_utf8);
 
     cache_re(prog);
 #ifdef DEBUGGING
@@ -1613,7 +1643,7 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
 
     minlen = prog->minlen;
     if (strend - startpos < minlen) {
-        DEBUG_r(PerlIO_printf(Perl_debug_log,
+        DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log,
                              "String too short [regexec_flags]...\n"));
        goto phooey;
     }
@@ -1667,32 +1697,32 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
            PL_reg_ganch = strbeg;
     }
 
-    if (!(flags & REXEC_CHECKED) && (prog->check_substr != Nullsv || prog->check_utf8 != Nullsv)) {
+    if (!(flags & REXEC_CHECKED) && (prog->check_substr != NULL || prog->check_utf8 != NULL)) {
        re_scream_pos_data d;
 
        d.scream_olds = &scream_olds;
        d.scream_pos = &scream_pos;
        s = re_intuit_start(prog, sv, s, strend, flags, &d);
        if (!s) {
-           DEBUG_r(PerlIO_printf(Perl_debug_log, "Not present...\n"));
+           DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "Not present...\n"));
            goto phooey;        /* not present */
        }
     }
 
-    DEBUG_r({
-        char *s0   = UTF ?
-          pv_uni_display(dsv0, (U8*)prog->precomp, prog->prelen, 60,
-                         UNI_DISPLAY_REGEX) :
-          prog->precomp;
-        int   len0 = UTF ? SvCUR(dsv0) : prog->prelen;
-        char *s1   = do_utf8 ? sv_uni_display(dsv1, sv, 60,
+    DEBUG_EXECUTE_r({
+       const char * const s0   = UTF
+           ? pv_uni_display(dsv0, (U8*)prog->precomp, prog->prelen, 60,
+                         UNI_DISPLAY_REGEX)
+           : prog->precomp;
+       const int len0 = UTF ? SvCUR(dsv0) : prog->prelen;
+       const char * const s1 = do_utf8 ? sv_uni_display(dsv1, sv, 60,
                                               UNI_DISPLAY_REGEX) : startpos;
-        int   len1 = do_utf8 ? SvCUR(dsv1) : strend - startpos;
+       const int len1 = do_utf8 ? SvCUR(dsv1) : strend - startpos;
         if (!PL_colorset)
             reginitcolors();
         PerlIO_printf(Perl_debug_log,
-                      "%sMatching REx%s `%s%*.*s%s%s' against `%s%.*s%s%s'\n",
-                      PL_colors[4],PL_colors[5],PL_colors[0],
+                      "%sMatching REx%s \"%s%*.*s%s%s\" against \"%s%.*s%s%s\"\n",
+                      PL_colors[4], PL_colors[5], PL_colors[0],
                       len0, len0, s0,
                       PL_colors[1],
                       len0 > 60 ? "..." : "",
@@ -1708,7 +1738,7 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
     if (prog->reganch & (ROPT_ANCH & ~ROPT_ANCH_GPOS)) {
        if (s == startpos && regtry(prog, startpos))
            goto got_it;
-       else if (PL_multiline || (prog->reganch & ROPT_IMPLICIT)
+       else if (multiline || (prog->reganch & ROPT_IMPLICIT)
                 || (prog->reganch & ROPT_ANCH_MBOL)) /* XXXX SBOL? */
        {
            char *end;
@@ -1762,12 +1792,12 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
 #endif
        if (!(do_utf8 ? prog->anchored_utf8 : prog->anchored_substr))
            do_utf8 ? to_utf8_substr(prog) : to_byte_substr(prog);
-       ch = SvPVX(do_utf8 ? prog->anchored_utf8 : prog->anchored_substr)[0];
+       ch = SvPVX_const(do_utf8 ? prog->anchored_utf8 : prog->anchored_substr)[0];
 
        if (do_utf8) {
            while (s < strend) {
                if (*s == ch) {
-                   DEBUG_r( did_match = 1 );
+                   DEBUG_EXECUTE_r( did_match = 1 );
                    if (regtry(prog, s)) goto got_it;
                    s += UTF8SKIP(s);
                    while (s < strend && *s == ch)
@@ -1779,7 +1809,7 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
        else {
            while (s < strend) {
                if (*s == ch) {
-                   DEBUG_r( did_match = 1 );
+                   DEBUG_EXECUTE_r( did_match = 1 );
                    if (regtry(prog, s)) goto got_it;
                    s++;
                    while (s < strend && *s == ch)
@@ -1788,15 +1818,14 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
                s++;
            }
        }
-       DEBUG_r(if (!did_match)
+       DEBUG_EXECUTE_r(if (!did_match)
                PerlIO_printf(Perl_debug_log,
                                   "Did not find anchored character...\n")
                );
     }
-    /*SUPPRESS 560*/
-    else if (prog->anchored_substr != Nullsv
-             || prog->anchored_utf8 != Nullsv
-             || ((prog->float_substr != Nullsv || prog->float_utf8 != Nullsv)
+    else if (prog->anchored_substr != NULL
+             || prog->anchored_utf8 != NULL
+             || ((prog->float_substr != NULL || prog->float_utf8 != NULL)
                  && prog->float_max_offset < strend - s)) {
        SV *must;
        I32 back_max;
@@ -1831,7 +1860,7 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
        else
            last1 = s - 1;      /* bogus */
 
-       /* XXXX check_substr already used to find `s', can optimize if
+       /* XXXX check_substr already used to find "s", can optimize if
           check_substr==must. */
        scream_pos = -1;
        dontbother = end_shift;
@@ -1842,17 +1871,20 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
                                    end_shift, &scream_pos, 0))
                 : (s = fbm_instr((unsigned char*)HOP3(s, back_min, strend),
                                  (unsigned char*)strend, must,
-                                 PL_multiline ? FBMrf_MULTILINE : 0))) ) {
-           DEBUG_r( did_match = 1 );
+                                 multiline ? FBMrf_MULTILINE : 0))) ) {
+           /* we may be pointing at the wrong string */
+           if ((flags & REXEC_SCREAM) && RX_MATCH_COPIED(prog))
+               s = strbeg + (s - SvPVX_const(sv));
+           DEBUG_EXECUTE_r( did_match = 1 );
            if (HOPc(s, -back_max) > last1) {
                last1 = HOPc(s, -back_min);
                s = HOPc(s, -back_max);
            }
            else {
-               char *t = (last1 >= PL_bostr) ? HOPc(last1, 1) : last1 + 1;
+               char * const t = (last1 >= PL_bostr) ? HOPc(last1, 1) : last1 + 1;
 
                last1 = HOPc(s, -back_min);
-               s = t;          
+               s = t;
            }
            if (do_utf8) {
                while (s <= last1) {
@@ -1869,50 +1901,53 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
                }
            }
        }
-       DEBUG_r(if (!did_match)
+       DEBUG_EXECUTE_r(if (!did_match)
                     PerlIO_printf(Perl_debug_log, 
-                                  "Did not find %s substr `%s%.*s%s'%s...\n",
+                                  "Did not find %s substr \"%s%.*s%s\"%s...\n",
                              ((must == prog->anchored_substr || must == prog->anchored_utf8)
                               ? "anchored" : "floating"),
                              PL_colors[0],
                              (int)(SvCUR(must) - (SvTAIL(must)!=0)),
-                             SvPVX(must),
+                             SvPVX_const(must),
                                   PL_colors[1], (SvTAIL(must) ? "$" : ""))
                );
        goto phooey;
     }
     else if ((c = prog->regstclass)) {
-       if (minlen && PL_regkind[(U8)OP(prog->regstclass)] != EXACT)
+       if (minlen) {
+           I32 op = (U8)OP(prog->regstclass);
            /* don't bother with what can't match */
-           strend = HOPc(strend, -(minlen - 1));
-       DEBUG_r({
+           if (PL_regkind[op] != EXACT && op != CANY)
+               strend = HOPc(strend, -(minlen - 1));
+       }
+       DEBUG_EXECUTE_r({
            SV *prop = sv_newmortal();
-           char *s0;
-           char *s1;
+           const char *s0;
+           const char *s1;
            int len0;
            int len1;
 
            regprop(prop, c);
            s0 = UTF ?
-             pv_uni_display(dsv0, (U8*)SvPVX(prop), SvCUR(prop), 60,
+             pv_uni_display(dsv0, (U8*)SvPVX_const(prop), SvCUR(prop), 60,
                             UNI_DISPLAY_REGEX) :
-             SvPVX(prop);
+             SvPVX_const(prop);
            len0 = UTF ? SvCUR(dsv0) : SvCUR(prop);
            s1 = UTF ?
              sv_uni_display(dsv1, sv, 60, UNI_DISPLAY_REGEX) : s;
            len1 = UTF ? SvCUR(dsv1) : strend - s;
            PerlIO_printf(Perl_debug_log,
-                         "Matching stclass `%*.*s' against `%*.*s'\n",
+                         "Matching stclass \"%*.*s\" against \"%*.*s\"\n",
                          len0, len0, s0,
                          len1, len1, s1);
        });
-       if (find_byclass(prog, c, s, strend, startpos, 0))
+        if (find_byclass(prog, c, s, strend, 0))
            goto got_it;
-       DEBUG_r(PerlIO_printf(Perl_debug_log, "Contradicts stclass...\n"));
+       DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "Contradicts stclass...\n"));
     }
     else {
        dontbother = 0;
-       if (prog->float_substr != Nullsv || prog->float_utf8 != Nullsv) {
+       if (prog->float_substr != NULL || prog->float_utf8 != NULL) {
            /* Trim the end. */
            char *last;
            SV* float_real;
@@ -1926,17 +1961,20 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
                                   end_shift, &scream_pos, 1); /* last one */
                if (!last)
                    last = scream_olds; /* Only one occurrence. */
+               /* we may be pointing at the wrong string */
+               else if (RX_MATCH_COPIED(prog))
+                   s = strbeg + (s - SvPVX_const(sv));
            }
            else {
                STRLEN len;
-               char *little = SvPV(float_real, len);
+                const char * const little = SvPV_const(float_real, len);
 
                if (SvTAIL(float_real)) {
                    if (memEQ(strend - len + 1, little, len - 1))
                        last = strend - len + 1;
-                   else if (!PL_multiline)
+                   else if (!multiline)
                        last = memEQ(strend - len, little, len)
-                           ? strend - len : Nullch;
+                           ? strend - len : NULL;
                    else
                        goto find_last;
                } else {
@@ -1944,13 +1982,13 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
                    if (len)
                        last = rninstr(s, strend, little, little + len);
                    else
-                       last = strend;  /* matching `$' */
+                       last = strend;  /* matching "$" */
                }
            }
            if (last == NULL) {
-               DEBUG_r(PerlIO_printf(Perl_debug_log,
+               DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log,
                                      "%sCan't trim the tail, match fails (should not happen)%s\n",
-                                     PL_colors[4],PL_colors[5]));
+                                     PL_colors[4], PL_colors[5]));
                goto phooey; /* Should not happen! */
            }
            dontbother = strend - last + prog->float_min_offset;
@@ -1993,17 +2031,28 @@ got_it:
 
     /* make sure $`, $&, $', and $digit will work later */
     if ( !(flags & REXEC_NOT_FIRST) ) {
-       if (RX_MATCH_COPIED(prog)) {
-           Safefree(prog->subbeg);
-           RX_MATCH_COPIED_off(prog);
-       }
+       RX_MATCH_COPY_FREE(prog);
        if (flags & REXEC_COPY_STR) {
            I32 i = PL_regeol - startpos + (stringarg - strbeg);
-
-           s = savepvn(strbeg, i);
-           prog->subbeg = s;
+#ifdef PERL_OLD_COPY_ON_WRITE
+           if ((SvIsCOW(sv)
+                || (SvFLAGS(sv) & CAN_COW_MASK) == CAN_COW_FLAGS)) {
+               if (DEBUG_C_TEST) {
+                   PerlIO_printf(Perl_debug_log,
+                                 "Copy on write: regexp capture, type %d\n",
+                                 (int) SvTYPE(sv));
+               }
+               prog->saved_copy = sv_setsv_cow(prog->saved_copy, sv);
+               prog->subbeg = (char *)SvPVX_const(prog->saved_copy);
+               assert (SvPOKp(prog->saved_copy));
+           } else
+#endif
+           {
+               RX_MATCH_COPIED_on(prog);
+               s = savepvn(strbeg, i);
+               prog->subbeg = s;
+           }
            prog->sublen = i;
-           RX_MATCH_COPIED_on(prog);
        }
        else {
            prog->subbeg = strbeg;
@@ -2014,8 +2063,8 @@ got_it:
     return 1;
 
 phooey:
-    DEBUG_r(PerlIO_printf(Perl_debug_log, "%sMatch failed%s\n",
-                         PL_colors[4],PL_colors[5]));
+    DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "%sMatch failed%s\n",
+                         PL_colors[4], PL_colors[5]));
     if (PL_reg_eval_set)
        restore_pos(aTHX_ 0);
     return 0;
@@ -2027,10 +2076,12 @@ phooey:
 STATIC I32                     /* 0 failure, 1 success */
 S_regtry(pTHX_ regexp *prog, char *startpos)
 {
+    dVAR;
     register I32 i;
     register I32 *sp;
     register I32 *ep;
     CHECKPOINT lastcp;
+    GET_RE_DEBUG_FLAGS_DECL;
 
 #ifdef DEBUGGING
     PL_regindent = 0;  /* XXXX Not good when matches are reenterable... */
@@ -2039,7 +2090,7 @@ S_regtry(pTHX_ regexp *prog, char *startpos)
        MAGIC *mg;
 
        PL_reg_eval_set = RS_init;
-       DEBUG_r(DEBUG_s(
+       DEBUG_EXECUTE_r(DEBUG_s(
            PerlIO_printf(Perl_debug_log, "  setting stack tmpbase at %"IVdf"\n",
                          (IV)(PL_stack_sp - PL_stack_base));
            ));
@@ -2054,17 +2105,19 @@ S_regtry(pTHX_ regexp *prog, char *startpos)
        if (PL_reg_sv) {
            /* Make $_ available to executed code. */
            if (PL_reg_sv != DEFSV) {
-               /* SAVE_DEFSV does *not* suffice here for USE_5005THREADS */
-               SAVESPTR(DEFSV);
+               SAVE_DEFSV;
                DEFSV = PL_reg_sv;
            }
        
            if (!(SvTYPE(PL_reg_sv) >= SVt_PVMG && SvMAGIC(PL_reg_sv)
                  && (mg = mg_find(PL_reg_sv, PERL_MAGIC_regex_global)))) {
                /* prepare for quick setting of pos */
-               sv_magic(PL_reg_sv, (SV*)0,
-                       PERL_MAGIC_regex_global, Nullch, 0);
-               mg = mg_find(PL_reg_sv, PERL_MAGIC_regex_global);
+#ifdef PERL_OLD_COPY_ON_WRITE
+               if (SvIsCOW(sv))
+                   sv_force_normal_flags(sv, 0);
+#endif
+               mg = sv_magicext(PL_reg_sv, (SV*)0, PERL_MAGIC_regex_global,
+                                &PL_vtbl_mglob, NULL, 0);
                mg->mg_len = -1;
            }
            PL_reg_magic    = mg;
@@ -2072,7 +2125,7 @@ S_regtry(pTHX_ regexp *prog, char *startpos)
            SAVEDESTRUCTOR_X(restore_pos, 0);
         }
         if (!PL_reg_curpm) {
-           Newz(22,PL_reg_curpm, 1, PMOP);
+           Newxz(PL_reg_curpm, 1, PMOP);
 #ifdef USE_ITHREADS
             {
                 SV* repointer = newSViv(0);
@@ -2093,10 +2146,13 @@ S_regtry(pTHX_ regexp *prog, char *startpos)
                $` inside (?{}) could fail... */
            PL_reg_oldsaved = prog->subbeg;
            PL_reg_oldsavedlen = prog->sublen;
+#ifdef PERL_OLD_COPY_ON_WRITE
+           PL_nrs = prog->saved_copy;
+#endif
            RX_MATCH_COPIED_off(prog);
        }
        else
-           PL_reg_oldsaved = Nullch;
+           PL_reg_oldsaved = NULL;
        prog->subbeg = PL_bostr;
        prog->sublen = PL_regeol - PL_bostr; /* strend may have been modified */
     }
@@ -2107,14 +2163,15 @@ S_regtry(pTHX_ regexp *prog, char *startpos)
     PL_reglastparen = &prog->lastparen;
     PL_reglastcloseparen = &prog->lastcloseparen;
     prog->lastparen = 0;
+    prog->lastcloseparen = 0;
     PL_regsize = 0;
-    DEBUG_r(PL_reg_starttry = startpos);
+    DEBUG_EXECUTE_r(PL_reg_starttry = startpos);
     if (PL_reg_start_tmpl <= prog->nparens) {
        PL_reg_start_tmpl = prog->nparens*3/2 + 3;
         if(PL_reg_start_tmp)
             Renew(PL_reg_start_tmp, PL_reg_start_tmpl, char*);
         else
-            New(22,PL_reg_start_tmp, PL_reg_start_tmpl, char*);
+            Newx(PL_reg_start_tmp, PL_reg_start_tmpl, char*);
     }
 
     /* XXXX What this code is doing here?!!!  There should be no need
@@ -2189,7 +2246,78 @@ typedef union re_unwind_t {
 #define sayNO_SILENT goto do_no
 #define saySAME(x) if (x) goto yes; else goto no
 
-#define REPORT_CODE_OFF 24
+#define POSCACHE_SUCCESS 0     /* caching success rather than failure */
+#define POSCACHE_SEEN 1                /* we know what we're caching */
+#define POSCACHE_START 2       /* the real cache: this bit maps to pos 0 */
+#define CACHEsayYES STMT_START { \
+    if (st->whilem.cache_offset | st->whilem.cache_bit) { \
+       if (!(PL_reg_poscache[0] & (1<<POSCACHE_SEEN))) \
+           PL_reg_poscache[0] |= (1<<POSCACHE_SUCCESS) || (1<<POSCACHE_SEEN); \
+        else if (!(PL_reg_poscache[0] & (1<<POSCACHE_SUCCESS))) { \
+           /* cache records failure, but this is success */ \
+           DEBUG_r( \
+               PerlIO_printf(Perl_debug_log, \
+                   "%*s  (remove success from failure cache)\n", \
+                   REPORT_CODE_OFF+PL_regindent*2, "") \
+           ); \
+           PL_reg_poscache[st->whilem.cache_offset] &= ~(1<<st->whilem.cache_bit); \
+       } \
+    } \
+    sayYES; \
+} STMT_END
+#define CACHEsayNO STMT_START { \
+    if (st->whilem.cache_offset | st->whilem.cache_bit) { \
+       if (!(PL_reg_poscache[0] & (1<<POSCACHE_SEEN))) \
+           PL_reg_poscache[0] |= (1<<POSCACHE_SEEN); \
+        else if ((PL_reg_poscache[0] & (1<<POSCACHE_SUCCESS))) { \
+           /* cache records success, but this is failure */ \
+           DEBUG_r( \
+               PerlIO_printf(Perl_debug_log, \
+                   "%*s  (remove failure from success cache)\n", \
+                   REPORT_CODE_OFF+PL_regindent*2, "") \
+           ); \
+           PL_reg_poscache[st->whilem.cache_offset] &= ~(1<<st->whilem.cache_bit); \
+       } \
+    } \
+    sayNO; \
+} STMT_END
+
+/* this is used to determine how far from the left messages like
+   'failed...' are printed. Currently 29 makes these messages line
+   up with the opcode they refer to. Earlier perls used 25 which
+   left these messages outdented making reviewing a debug output
+   quite difficult.
+*/
+#define REPORT_CODE_OFF 29
+
+
+/* Make sure there is a test for this +1 options in re_tests */
+#define TRIE_INITAL_ACCEPT_BUFFLEN 4;
+
+/* grab a new slab and return the first slot in it */
+
+STATIC regmatch_state *
+S_push_slab(pTHX)
+{
+    regmatch_slab *s = PL_regmatch_slab->next;
+    if (!s) {
+       Newx(s, 1, regmatch_slab);
+       s->prev = PL_regmatch_slab;
+       s->next = NULL;
+       PL_regmatch_slab->next = s;
+    }
+    PL_regmatch_slab = s;
+    return &s->states[0];
+}
+
+/* simulate a recursive call to regmatch */
+
+#define REGMATCH(ns, where) \
+    st->scan = scan; \
+    scan = (ns); \
+    st->resume_state = resume_##where; \
+    goto start_recurse; \
+    resume_point_##where:
 
 /*
  - regmatch - main matching routine
@@ -2204,45 +2332,162 @@ typedef union re_unwind_t {
 /* [lwall] I've hoisted the register declarations to the outer block in order to
  * maybe save a little bit of pushing and popping on the stack.  It also takes
  * advantage of machines that use a register save mask on subroutine entry.
+ *
+ * This function used to be heavily recursive, but since this had the
+ * effect of blowing the CPU stack on complex regexes, it has been
+ * restructured to be iterative, and to save state onto the heap rather
+ * than the stack. Essentially whereever regmatch() used to be called, it
+ * pushes the current state, notes where to return, then jumps back into
+ * the main loop.
+ *
+ * Originally the structure of this function used to look something like
+
+    S_regmatch() {
+       int a = 1, b = 2;
+       ...
+       while (scan != NULL) {
+           a++; // do stuff with a and b
+           ...
+           switch (OP(scan)) {
+               case FOO: {
+                   int local = 3;
+                   ...
+                   if (regmatch(...))  // recurse
+                       goto yes;
+               }
+               ...
+           }
+       }
+       yes:
+       return 1;
+    }
+
+ * Now it looks something like this:
+
+    typedef struct {
+       int a, b, local;
+       int resume_state;
+    } regmatch_state;
+
+    S_regmatch() {
+       regmatch_state *st = new();
+       int depth=0;
+       st->a++; // do stuff with a and b
+       ...
+       while (scan != NULL) {
+           ...
+           switch (OP(scan)) {
+               case FOO: {
+                   st->local = 3;
+                   ...
+                   st->scan = scan;
+                   scan = ...;
+                   st->resume_state = resume_FOO;
+                   goto start_recurse; // recurse
+
+                   resume_point_FOO:
+                   if (result)
+                       goto yes;
+               }
+               ...
+           }
+         start_recurse:
+           st = new(); push a new state
+           st->a = 1; st->b = 2;
+           depth++;
+       }
+      yes:
+       result = 1;
+       if (depth--) {
+           st = pop();
+           switch (resume_state) {
+           case resume_FOO:
+               goto resume_point_FOO;
+           ...
+           }
+       }
+       return result
+    }
+           
+ * WARNING: this means that any line in this function that contains a
+ * REGMATCH() or TRYPAREN() is actually simulating a recursive call to
+ * regmatch() using gotos instead. Thus the values of any local variables
+ * not saved in the regmatch_state structure will have been lost when
+ * execution resumes on the next line .
+ *
+ * States (ie the st pointer) are allocated in slabs of about 4K in size.
+ * PL_regmatch_state always points to the currently active state, and
+ * PL_regmatch_slab points to the slab currently containing PL_regmatch_state.
+ * The first time regmatch is called, the first slab is allocated, and is
+ * never freed until interpreter desctruction. When the slab is full,
+ * a new one is allocated chained to the end. At exit from regmatch, slabs
+ * allocated since entry are freed.
  */
+
 STATIC I32                     /* 0 failure, 1 success */
 S_regmatch(pTHX_ regnode *prog)
 {
-    register regnode *scan;    /* Current node. */
-    regnode *next;             /* Next node. */
-    regnode *inner;            /* Next node in internal branch. */
-    register I32 nextchr;      /* renamed nextchr - nextchar colides with
-                                  function of same name */
-    register I32 n;            /* no or next */
-    register I32 ln = 0;       /* len or last */
-    register char *s = Nullch; /* operand or save */
+    dVAR;
+    register const bool do_utf8 = PL_reg_match_utf8;
+    const U32 uniflags = ckWARN(WARN_UTF8) ? 0 : UTF8_ALLOW_ANY;
+
+    regmatch_slab  *orig_slab;
+    regmatch_state *orig_state;
+
+    /* the current state. This is a cached copy of PL_regmatch_state */
+    register regmatch_state *st;
+
+    /* cache heavy used fields of st in registers */
+    register regnode *scan;
+    register regnode *next;
+    register I32 n = 0;        /* initialize to shut up compiler warning */
     register char *locinput = PL_reginput;
-    register I32 c1 = 0, c2 = 0, paren;        /* case fold search, parenth */
-    int minmod = 0, sw = 0, logical = 0;
-    I32 unwind = 0;
-#if 0
-    I32 firstcp = PL_savestack_ix;
-#endif
-    register bool do_utf8 = PL_reg_match_utf8;
-#ifdef DEBUGGING
-    SV *dsv0 = PERL_DEBUG_PAD_ZERO(0);
-    SV *dsv1 = PERL_DEBUG_PAD_ZERO(1);
-    SV *dsv2 = PERL_DEBUG_PAD_ZERO(2);
-#endif
 
+    /* these variables are NOT saved during a recusive RFEGMATCH: */
+    register I32 nextchr;   /* is always set to UCHARAT(locinput) */
+    bool result;           /* return value of S_regmatch */
+    regnode *inner;        /* Next node in internal branch. */
+    int depth = 0;         /* depth of recursion */
+    
 #ifdef DEBUGGING
+    SV *re_debug_flags = NULL;
+    GET_RE_DEBUG_FLAGS;
     PL_regindent++;
 #endif
 
+    /* on first ever call to regmatch, allocate first slab */
+    if (!PL_regmatch_slab) {
+       Newx(PL_regmatch_slab, 1, regmatch_slab);
+       PL_regmatch_slab->prev = NULL;
+       PL_regmatch_slab->next = NULL;
+       PL_regmatch_state = &PL_regmatch_slab->states[0] - 1;
+    }
+
+    /* remember current high-water mark for exit */
+    /* XXX this should be done with SAVE* instead */
+    orig_slab  = PL_regmatch_slab;
+    orig_state = PL_regmatch_state;
+
+    /* grab next free state slot */
+    st = ++PL_regmatch_state;
+    if (st >  &(PL_regmatch_slab->states[PERL_REGMATCH_SLAB_SLOTS-1]))
+       st = PL_regmatch_state = S_push_slab(aTHX);
+
+    st->minmod = 0;
+    st->sw = 0;
+    st->logical = 0;
+    st->unwind = 0;
+    st->cc = NULL;
     /* Note that nextchr is a byte even in UTF */
     nextchr = UCHARAT(locinput);
     scan = prog;
     while (scan != NULL) {
 
-        DEBUG_r( {
-           SV *prop = sv_newmortal();
-           int docolor = *PL_colors[0];
-           int taill = (docolor ? 10 : 7); /* 3 chars for "> <" */
+        DEBUG_EXECUTE_r( {
+           SV * const prop = sv_newmortal();
+           const int docolor = *PL_colors[0];
+           const int taill = (docolor ? 10 : 7); /* 3 chars for "> <" */
            int l = (PL_regeol - locinput) > taill ? taill : (PL_regeol - locinput);
            /* The part of the string before starttry has one color
               (pref0_len chars), between starttry and current
@@ -2268,22 +2513,23 @@ S_regmatch(pTHX_ regnode *prog)
                pref0_len = pref_len;
            regprop(prop, scan);
            {
-             char *s0 =
-               do_utf8 ?
-               pv_uni_display(dsv0, (U8*)(locinput - pref_len),
+             const char * const s0 =
+               do_utf8 && OP(scan) != CANY ?
+               pv_uni_display(PERL_DEBUG_PAD(0), (U8*)(locinput - pref_len),
                               pref0_len, 60, UNI_DISPLAY_REGEX) :
                locinput - pref_len;
-             int len0 = do_utf8 ? strlen(s0) : pref0_len;
-             char *s1 = do_utf8 ?
-               pv_uni_display(dsv1, (U8*)(locinput - pref_len + pref0_len),
+             const int len0 = do_utf8 ? strlen(s0) : pref0_len;
+             const char * const s1 = do_utf8 && OP(scan) != CANY ?
+               pv_uni_display(PERL_DEBUG_PAD(1),
+                              (U8*)(locinput - pref_len + pref0_len),
                               pref_len - pref0_len, 60, UNI_DISPLAY_REGEX) :
                locinput - pref_len + pref0_len;
-             int len1 = do_utf8 ? strlen(s1) : pref_len - pref0_len;
-             char *s2 = do_utf8 ?
-               pv_uni_display(dsv2, (U8*)locinput,
+             const int len1 = do_utf8 ? strlen(s1) : pref_len - pref0_len;
+             const char * const s2 = do_utf8 && OP(scan) != CANY ?
+               pv_uni_display(PERL_DEBUG_PAD(2), (U8*)locinput,
                               PL_regeol - locinput, 60, UNI_DISPLAY_REGEX) :
                locinput;
-             int len2 = do_utf8 ? strlen(s2) : l;
+             const int len2 = do_utf8 ? strlen(s2) : l;
              PerlIO_printf(Perl_debug_log,
                            "%4"IVdf" <%s%.*s%s%s%.*s%s%s%s%.*s%s>%*s|%3"IVdf":%*s%s\n",
                            (IV)(locinput - PL_bostr),
@@ -2300,7 +2546,7 @@ S_regmatch(pTHX_ regnode *prog)
                            15 - l - pref_len + 1,
                            "",
                            (IV)(scan - PL_regprogram), PL_regindent*2, "",
-                           SvPVX(prop));
+                           SvPVX_const(prop));
            }
        });
 
@@ -2310,8 +2556,7 @@ S_regmatch(pTHX_ regnode *prog)
 
        switch (OP(scan)) {
        case BOL:
-           if (locinput == PL_bostr || (PL_multiline &&
-               (nextchr || locinput < PL_regeol) && locinput[-1] == '\n') )
+           if (locinput == PL_bostr)
            {
                /* regtill = regbol; */
                break;
@@ -2333,12 +2578,8 @@ S_regmatch(pTHX_ regnode *prog)
                break;
            sayNO;
        case EOL:
-           if (PL_multiline)
-               goto meol;
-           else
                goto seol;
        case MEOL:
-         meol:
            if ((nextchr || locinput < PL_regeol) && nextchr != '\n')
                sayNO;
            break;
@@ -2382,24 +2623,253 @@ S_regmatch(pTHX_ regnode *prog)
            else
                nextchr = UCHARAT(++locinput);
            break;
-       case EXACT:
-           s = STRING(scan);
-           ln = STR_LEN(scan);
+
+
+
+       /*
+          traverse the TRIE keeping track of all accepting states
+          we transition through until we get to a failing node.
+
+
+       */
+       case TRIE:
+       case TRIEF:
+       case TRIEFL:
+           {
+               U8 *uc = ( U8* )locinput;
+               U32 state = 1;
+               U16 charid = 0;
+               U32 base = 0;
+               UV uvc = 0;
+               STRLEN len = 0;
+               STRLEN foldlen = 0;
+               U8 *uscan = (U8*)NULL;
+               STRLEN bufflen=0;
+               SV *sv_accept_buff = NULL;
+               const enum { trie_plain, trie_utf8, trie_uft8_fold }
+                   trie_type = do_utf8 ?
+                         (OP(scan) == TRIE ? trie_utf8 : trie_uft8_fold)
+                       : trie_plain;
+
+               /* what trie are we using right now */
+               reg_trie_data *trie
+                   = (reg_trie_data*)PL_regdata->data[ ARG( scan ) ];
+               st->trie.accepted = 0; /* how many accepting states we have seen */
+               result = 0;
+
+               while ( state && uc <= (U8*)PL_regeol ) {
+
+                   if (trie->states[ state ].wordnum) {
+                       if (!st->trie.accepted ) {
+                           ENTER;
+                           SAVETMPS;
+                           bufflen = TRIE_INITAL_ACCEPT_BUFFLEN;
+                           sv_accept_buff=newSV(bufflen *
+                                           sizeof(reg_trie_accepted) - 1);
+                           SvCUR_set(sv_accept_buff,
+                                               sizeof(reg_trie_accepted));
+                           SvPOK_on(sv_accept_buff);
+                           sv_2mortal(sv_accept_buff);
+                           st->trie.accept_buff =
+                               (reg_trie_accepted*)SvPV_nolen(sv_accept_buff );
+                       }
+                       else {
+                           if (st->trie.accepted >= bufflen) {
+                               bufflen *= 2;
+                               st->trie.accept_buff =(reg_trie_accepted*)
+                                   SvGROW(sv_accept_buff,
+                                       bufflen * sizeof(reg_trie_accepted));
+                           }
+                           SvCUR_set(sv_accept_buff,SvCUR(sv_accept_buff)
+                               + sizeof(reg_trie_accepted));
+                       }
+                       st->trie.accept_buff[st->trie.accepted].wordnum = trie->states[state].wordnum;
+                       st->trie.accept_buff[st->trie.accepted].endpos = uc;
+                       ++st->trie.accepted;
+                   }
+
+                   base = trie->states[ state ].trans.base;
+
+                   DEBUG_TRIE_EXECUTE_r(
+                               PerlIO_printf( Perl_debug_log,
+                                   "%*s  %sState: %4"UVxf", Base: %4"UVxf", Accepted: %4"UVxf" ",
+                                   REPORT_CODE_OFF + PL_regindent * 2, "", PL_colors[4],
+                                   (UV)state, (UV)base, (UV)st->trie.accepted );
+                   );
+
+                   if ( base ) {
+                       switch (trie_type) {
+                       case trie_uft8_fold:
+                           if ( foldlen>0 ) {
+                               uvc = utf8n_to_uvuni( uscan, UTF8_MAXLEN, &len, uniflags );
+                               foldlen -= len;
+                               uscan += len;
+                               len=0;
+                           } else {
+                               U8 foldbuf[ UTF8_MAXBYTES_CASE + 1 ];
+                               uvc = utf8n_to_uvuni( (U8*)uc, UTF8_MAXLEN, &len, uniflags );
+                               uvc = to_uni_fold( uvc, foldbuf, &foldlen );
+                               foldlen -= UNISKIP( uvc );
+                               uscan = foldbuf + UNISKIP( uvc );
+                           }
+                           break;
+                       case trie_utf8:
+                           uvc = utf8n_to_uvuni( (U8*)uc, UTF8_MAXLEN,
+                                                           &len, uniflags );
+                           break;
+                       case trie_plain:
+                           uvc = (UV)*uc;
+                           len = 1;
+                       }
+
+                       if (uvc < 256) {
+                           charid = trie->charmap[ uvc ];
+                       }
+                       else {
+                           charid = 0;
+                           if (trie->widecharmap) {
+                               SV** svpp = (SV**)NULL;
+                               svpp = hv_fetch(trie->widecharmap,
+                                           (char*)&uvc, sizeof(UV), 0);
+                               if (svpp)
+                                   charid = (U16)SvIV(*svpp);
+                           }
+                       }
+
+                       if (charid &&
+                            (base + charid > trie->uniquecharcount )
+                            && (base + charid - 1 - trie->uniquecharcount
+                                   < trie->lasttrans)
+                            && trie->trans[base + charid - 1 -
+                                   trie->uniquecharcount].check == state)
+                       {
+                           state = trie->trans[base + charid - 1 -
+                               trie->uniquecharcount ].next;
+                       }
+                       else {
+                           state = 0;
+                       }
+                       uc += len;
+
+                   }
+                   else {
+                       state = 0;
+                   }
+                   DEBUG_TRIE_EXECUTE_r(
+                       PerlIO_printf( Perl_debug_log,
+                           "Charid:%3x CV:%4"UVxf" After State: %4"UVxf"%s\n",
+                           charid, uvc, (UV)state, PL_colors[5] );
+                   );
+               }
+               if (!st->trie.accepted )
+                  sayNO;
+
+           /*
+              There was at least one accepting state that we
+              transitioned through. Presumably the number of accepting
+              states is going to be low, typically one or two. So we
+              simply scan through to find the one with lowest wordnum.
+              Once we find it, we swap the last state into its place
+              and decrement the size. We then try to match the rest of
+              the pattern at the point where the word ends, if we
+              succeed then we end the loop, otherwise the loop
+              eventually terminates once all of the accepting states
+              have been tried.
+           */
+
+               if ( st->trie.accepted == 1 ) {
+                   DEBUG_EXECUTE_r({
+                        SV **tmp = av_fetch( trie->words, st->trie.accept_buff[ 0 ].wordnum-1, 0 );
+                               PerlIO_printf( Perl_debug_log,
+                           "%*s  %sonly one match : #%d <%s>%s\n",
+                           REPORT_CODE_OFF+PL_regindent*2, "", PL_colors[4],
+                           st->trie.accept_buff[ 0 ].wordnum,
+                           tmp ? SvPV_nolen_const( *tmp ) : "not compiled under -Dr",
+                           PL_colors[5] );
+                   });
+                   PL_reginput = (char *)st->trie.accept_buff[ 0 ].endpos;
+                   /* in this case we free tmps/leave before we call regmatch
+                      as we wont be using accept_buff again. */
+                   FREETMPS;
+                   LEAVE;
+                   REGMATCH(scan + NEXT_OFF(scan), TRIE1);
+                   /*** all unsaved local vars undefined at this point */
+               } else {
+                    DEBUG_EXECUTE_r(
+                        PerlIO_printf( Perl_debug_log,"%*s  %sgot %"IVdf" possible matches%s\n",
+                            REPORT_CODE_OFF + PL_regindent * 2, "", PL_colors[4], (IV)st->trie.accepted,
+                            PL_colors[5] );
+                    );
+                   while ( !result && st->trie.accepted-- ) {
+                       U32 best = 0;
+                       U32 cur;
+                       for( cur = 1 ; cur <= st->trie.accepted ; cur++ ) {
+                           DEBUG_TRIE_EXECUTE_r(
+                               PerlIO_printf( Perl_debug_log,
+                                   "%*s  %sgot %"IVdf" (%d) as best, looking at %"IVdf" (%d)%s\n",
+                                   REPORT_CODE_OFF + PL_regindent * 2, "", PL_colors[4],
+                                   (IV)best, st->trie.accept_buff[ best ].wordnum, (IV)cur,
+                                   st->trie.accept_buff[ cur ].wordnum, PL_colors[5] );
+                           );
+
+                           if (st->trie.accept_buff[cur].wordnum <
+                                   st->trie.accept_buff[best].wordnum)
+                               best = cur;
+                       }
+                       DEBUG_EXECUTE_r({
+                           SV ** const tmp = av_fetch( trie->words, st->trie.accept_buff[ best ].wordnum - 1, 0 );
+                           PerlIO_printf( Perl_debug_log, "%*s  %strying alternation #%d <%s> at 0x%p%s\n",
+                               REPORT_CODE_OFF+PL_regindent*2, "", PL_colors[4],
+                               st->trie.accept_buff[best].wordnum,
+                               tmp ? SvPV_nolen_const( *tmp ) : "not compiled under -Dr",scan,
+                               PL_colors[5] );
+                       });
+                       if ( best<st->trie.accepted ) {
+                           reg_trie_accepted tmp = st->trie.accept_buff[ best ];
+                           st->trie.accept_buff[ best ] = st->trie.accept_buff[ st->trie.accepted ];
+                           st->trie.accept_buff[ st->trie.accepted ] = tmp;
+                           best = st->trie.accepted;
+                       }
+                       PL_reginput = (char *)st->trie.accept_buff[ best ].endpos;
+
+                        /* 
+                           as far as I can tell we only need the SAVETMPS/FREETMPS 
+                           for re's with EVAL in them but I'm leaving them in for 
+                           all until I can be sure.
+                         */
+                       SAVETMPS;
+                       REGMATCH(scan + NEXT_OFF(scan), TRIE2);
+                       /*** all unsaved local vars undefined at this point */
+                       FREETMPS;
+                   }
+                   FREETMPS;
+                   LEAVE;
+               }
+               
+               if (result) {
+                   sayYES;
+               } else {
+                   sayNO;
+               }
+           }
+           /* unreached codepoint */
+       case EXACT: {
+           char *s = STRING(scan);
+           st->ln = STR_LEN(scan);
            if (do_utf8 != UTF) {
                /* The target and the pattern have differing utf8ness. */
                char *l = locinput;
-               char *e = s + ln;
-               STRLEN ulen;
+               const char *e = s + st->ln;
 
                if (do_utf8) {
                    /* The target is utf8, the pattern is not utf8. */
                    while (s < e) {
+                       STRLEN ulen;
                        if (l >= PL_regeol)
                             sayNO;
                        if (NATIVE_TO_UNI(*(U8*)s) !=
-                           utf8n_to_uvuni((U8*)l, UTF8_MAXLEN, &ulen,
-                                          ckWARN(WARN_UTF8) ?
-                                          0 : UTF8_ALLOW_ANY))
+                           utf8n_to_uvuni((U8*)l, UTF8_MAXBYTES, &ulen,
+                                           uniflags))
                             sayNO;
                        l += ulen;
                        s ++;
@@ -2408,12 +2878,12 @@ S_regmatch(pTHX_ regnode *prog)
                else {
                    /* The target is not utf8, the pattern is utf8. */
                    while (s < e) {
+                       STRLEN ulen;
                        if (l >= PL_regeol)
                            sayNO;
                        if (NATIVE_TO_UNI(*((U8*)l)) !=
-                           utf8n_to_uvuni((U8*)s, UTF8_MAXLEN, &ulen,
-                                          ckWARN(WARN_UTF8) ?
-                                          0 : UTF8_ALLOW_ANY))
+                           utf8n_to_uvuni((U8*)s, UTF8_MAXBYTES, &ulen,
+                                          uniflags))
                            sayNO;
                        s += ulen;
                        l ++;
@@ -2427,26 +2897,27 @@ S_regmatch(pTHX_ regnode *prog)
            /* Inline the first character, for speed. */
            if (UCHARAT(s) != nextchr)
                sayNO;
-           if (PL_regeol - locinput < ln)
+           if (PL_regeol - locinput < st->ln)
                sayNO;
-           if (ln > 1 && memNE(s, locinput, ln))
+           if (st->ln > 1 && memNE(s, locinput, st->ln))
                sayNO;
-           locinput += ln;
+           locinput += st->ln;
            nextchr = UCHARAT(locinput);
            break;
+           }
        case EXACTFL:
            PL_reg_flags |= RF_tainted;
            /* FALL THROUGH */
-       case EXACTF:
-           s = STRING(scan);
-           ln = STR_LEN(scan);
+       case EXACTF: {
+           char *s = STRING(scan);
+           st->ln = STR_LEN(scan);
 
            if (do_utf8 || UTF) {
              /* Either target or the pattern are utf8. */
                char *l = locinput;
                char *e = PL_regeol;
 
-               if (ibcmp_utf8(s, 0,  ln, (bool)UTF,
+               if (ibcmp_utf8(s, 0,  st->ln, (bool)UTF,
                               l, &e, 0,  do_utf8)) {
                     /* One more case for the sharp s:
                      * pack("U0U*", 0xDF) =~ /ss/i,
@@ -2454,7 +2925,7 @@ S_regmatch(pTHX_ regnode *prog)
                      * byte sequence for the U+00DF. */
                     if (!(do_utf8 &&
                           toLOWER(s[0]) == 's' &&
-                          ln >= 2 &&
+                          st->ln >= 2 &&
                           toLOWER(s[1]) == 's' &&
                           (U8)l[0] == 0xC3 &&
                           e - l >= 2 &&
@@ -2473,15 +2944,16 @@ S_regmatch(pTHX_ regnode *prog)
                UCHARAT(s) != ((OP(scan) == EXACTF)
                               ? PL_fold : PL_fold_locale)[nextchr])
                sayNO;
-           if (PL_regeol - locinput < ln)
+           if (PL_regeol - locinput < st->ln)
                sayNO;
-           if (ln > 1 && (OP(scan) == EXACTF
-                          ? ibcmp(s, locinput, ln)
-                          : ibcmp_locale(s, locinput, ln)))
+           if (st->ln > 1 && (OP(scan) == EXACTF
+                          ? ibcmp(s, locinput, st->ln)
+                          : ibcmp_locale(s, locinput, st->ln)))
                sayNO;
-           locinput += ln;
+           locinput += st->ln;
            nextchr = UCHARAT(locinput);
            break;
+           }
        case ANYOF:
            if (do_utf8) {
                STRLEN inclasslen = PL_regeol - locinput;
@@ -2522,7 +2994,7 @@ S_regmatch(pTHX_ regnode *prog)
            if (!nextchr)
                sayNO;
            if (do_utf8) {
-               LOAD_UTF8_CHARCLASS(alnum,"a");
+               LOAD_UTF8_CHARCLASS_ALNUM();
                if (!(OP(scan) == ALNUM
                      ? swash_fetch(PL_utf8_alnum, (U8*)locinput, do_utf8)
                      : isALNUM_LC_utf8((U8*)locinput)))
@@ -2545,7 +3017,7 @@ S_regmatch(pTHX_ regnode *prog)
            if (!nextchr && locinput >= PL_regeol)
                sayNO;
            if (do_utf8) {
-               LOAD_UTF8_CHARCLASS(alnum,"a");
+               LOAD_UTF8_CHARCLASS_ALNUM();
                if (OP(scan) == NALNUM
                    ? swash_fetch(PL_utf8_alnum, (U8*)locinput, do_utf8)
                    : isALNUM_LC_utf8((U8*)locinput))
@@ -2570,35 +3042,35 @@ S_regmatch(pTHX_ regnode *prog)
            /* was last char in word? */
            if (do_utf8) {
                if (locinput == PL_bostr)
-                   ln = '\n';
+                   st->ln = '\n';
                else {
-                   U8 *r = reghop3((U8*)locinput, -1, (U8*)PL_bostr);
+                   const U8 * const r = reghop3((U8*)locinput, -1, (U8*)PL_bostr);
                
-                   ln = utf8n_to_uvchr(r, UTF8SKIP(r), 0, 0);
+                   st->ln = utf8n_to_uvchr(r, UTF8SKIP(r), 0, 0);
                }
                if (OP(scan) == BOUND || OP(scan) == NBOUND) {
-                   ln = isALNUM_uni(ln);
-                   LOAD_UTF8_CHARCLASS(alnum,"a");
+                   st->ln = isALNUM_uni(st->ln);
+                   LOAD_UTF8_CHARCLASS_ALNUM();
                    n = swash_fetch(PL_utf8_alnum, (U8*)locinput, do_utf8);
                }
                else {
-                   ln = isALNUM_LC_uvchr(UNI_TO_NATIVE(ln));
+                   st->ln = isALNUM_LC_uvchr(UNI_TO_NATIVE(st->ln));
                    n = isALNUM_LC_utf8((U8*)locinput);
                }
            }
            else {
-               ln = (locinput != PL_bostr) ?
+               st->ln = (locinput != PL_bostr) ?
                    UCHARAT(locinput - 1) : '\n';
                if (OP(scan) == BOUND || OP(scan) == NBOUND) {
-                   ln = isALNUM(ln);
+                   st->ln = isALNUM(st->ln);
                    n = isALNUM(nextchr);
                }
                else {
-                   ln = isALNUM_LC(ln);
+                   st->ln = isALNUM_LC(st->ln);
                    n = isALNUM_LC(nextchr);
                }
            }
-           if (((!ln) == (!n)) == (OP(scan) == BOUND ||
+           if (((!st->ln) == (!n)) == (OP(scan) == BOUND ||
                                    OP(scan) == BOUNDL))
                    sayNO;
            break;
@@ -2610,7 +3082,7 @@ S_regmatch(pTHX_ regnode *prog)
                sayNO;
            if (do_utf8) {
                if (UTF8_IS_CONTINUED(nextchr)) {
-                   LOAD_UTF8_CHARCLASS(space," ");
+                   LOAD_UTF8_CHARCLASS_SPACE();
                    if (!(OP(scan) == SPACE
                          ? swash_fetch(PL_utf8_space, (U8*)locinput, do_utf8)
                          : isSPACE_LC_utf8((U8*)locinput)))
@@ -2640,7 +3112,7 @@ S_regmatch(pTHX_ regnode *prog)
            if (!nextchr && locinput >= PL_regeol)
                sayNO;
            if (do_utf8) {
-               LOAD_UTF8_CHARCLASS(space," ");
+               LOAD_UTF8_CHARCLASS_SPACE();
                if (OP(scan) == NSPACE
                    ? swash_fetch(PL_utf8_space, (U8*)locinput, do_utf8)
                    : isSPACE_LC_utf8((U8*)locinput))
@@ -2663,7 +3135,7 @@ S_regmatch(pTHX_ regnode *prog)
            if (!nextchr)
                sayNO;
            if (do_utf8) {
-               LOAD_UTF8_CHARCLASS(digit,"0");
+               LOAD_UTF8_CHARCLASS_DIGIT();
                if (!(OP(scan) == DIGIT
                      ? swash_fetch(PL_utf8_digit, (U8*)locinput, do_utf8)
                      : isDIGIT_LC_utf8((U8*)locinput)))
@@ -2686,7 +3158,7 @@ S_regmatch(pTHX_ regnode *prog)
            if (!nextchr && locinput >= PL_regeol)
                sayNO;
            if (do_utf8) {
-               LOAD_UTF8_CHARCLASS(digit,"0");
+               LOAD_UTF8_CHARCLASS_DIGIT();
                if (OP(scan) == NDIGIT
                    ? swash_fetch(PL_utf8_digit, (U8*)locinput, do_utf8)
                    : isDIGIT_LC_utf8((U8*)locinput))
@@ -2706,7 +3178,7 @@ S_regmatch(pTHX_ regnode *prog)
            if (locinput >= PL_regeol)
                sayNO;
            if  (do_utf8) {
-               LOAD_UTF8_CHARCLASS(mark,"~");
+               LOAD_UTF8_CHARCLASS_MARK();
                if (swash_fetch(PL_utf8_mark,(U8*)locinput, do_utf8))
                    sayNO;
                locinput += PL_utf8skip[nextchr];
@@ -2724,29 +3196,31 @@ S_regmatch(pTHX_ regnode *prog)
            PL_reg_flags |= RF_tainted;
            /* FALL THROUGH */
         case REF:
-       case REFF:
+       case REFF: {
+           char *s;
            n = ARG(scan);  /* which paren pair */
-           ln = PL_regstartp[n];
+           st->ln = PL_regstartp[n];
            PL_reg_leftiter = PL_reg_maxiter;           /* Void cache */
-           if ((I32)*PL_reglastparen < n || ln == -1)
+           if ((I32)*PL_reglastparen < n || st->ln == -1)
                sayNO;                  /* Do not match unless seen CLOSEn. */
-           if (ln == PL_regendp[n])
+           if (st->ln == PL_regendp[n])
                break;
 
-           s = PL_bostr + ln;
+           s = PL_bostr + st->ln;
            if (do_utf8 && OP(scan) != REF) {   /* REF can do byte comparison */
                char *l = locinput;
-               char *e = PL_bostr + PL_regendp[n];
+               const char *e = PL_bostr + PL_regendp[n];
                /*
                 * Note that we can't do the "other character" lookup trick as
                 * in the 8-bit case (no pun intended) because in Unicode we
                 * have to map both upper and title case to lower case.
                 */
                if (OP(scan) == REFF) {
-                   STRLEN ulen1, ulen2;
-                   U8 tmpbuf1[UTF8_MAXLEN_UCLC+1];
-                   U8 tmpbuf2[UTF8_MAXLEN_UCLC+1];
                    while (s < e) {
+                       STRLEN ulen1, ulen2;
+                       U8 tmpbuf1[UTF8_MAXBYTES_CASE+1];
+                       U8 tmpbuf2[UTF8_MAXBYTES_CASE+1];
+
                        if (l >= PL_regeol)
                            sayNO;
                        toLOWER_utf8((U8*)s, tmpbuf1, &ulen1);
@@ -2768,18 +3242,19 @@ S_regmatch(pTHX_ regnode *prog)
                 (UCHARAT(s) != ((OP(scan) == REFF
                                  ? PL_fold : PL_fold_locale)[nextchr]))))
                sayNO;
-           ln = PL_regendp[n] - ln;
-           if (locinput + ln > PL_regeol)
+           st->ln = PL_regendp[n] - st->ln;
+           if (locinput + st->ln > PL_regeol)
                sayNO;
-           if (ln > 1 && (OP(scan) == REF
-                          ? memNE(s, locinput, ln)
+           if (st->ln > 1 && (OP(scan) == REF
+                          ? memNE(s, locinput, st->ln)
                           : (OP(scan) == REFF
-                             ? ibcmp(s, locinput, ln)
-                             : ibcmp_locale(s, locinput, ln))))
+                             ? ibcmp(s, locinput, st->ln)
+                             : ibcmp_locale(s, locinput, st->ln))))
                sayNO;
-           locinput += ln;
+           locinput += st->ln;
            nextchr = UCHARAT(locinput);
            break;
+           }
 
        case NOTHING:
        case TAIL:
@@ -2789,19 +3264,20 @@ S_regmatch(pTHX_ regnode *prog)
        case EVAL:
        {
            dSP;
-           OP_4tree *oop = PL_op;
-           COP *ocurcop = PL_curcop;
-           SV **ocurpad = PL_curpad;
+           OP_4tree * const oop = PL_op;
+           COP * const ocurcop = PL_curcop;
+           PAD *old_comppad;
            SV *ret;
+           struct regexp * const oreg = PL_reg_re;
        
            n = ARG(scan);
            PL_op = (OP_4tree*)PL_regdata->data[n];
-           DEBUG_r( PerlIO_printf(Perl_debug_log, "  re_eval 0x%"UVxf"\n", PTR2UV(PL_op)) );
-           PL_curpad = AvARRAY((AV*)PL_regdata->data[n + 2]);
+           DEBUG_EXECUTE_r( PerlIO_printf(Perl_debug_log, "  re_eval 0x%"UVxf"\n", PTR2UV(PL_op)) );
+           PAD_SAVE_LOCAL(old_comppad, (PAD*)PL_regdata->data[n + 2]);
            PL_regendp[0] = PL_reg_magic->mg_len = locinput - PL_bostr;
 
            {
-               SV **before = SP;
+               SV ** const before = SP;
                CALLRUNOPS(aTHX);                       /* Scalar context. */
                SPAGAIN;
                if (SP == before)
@@ -2813,46 +3289,52 @@ S_regmatch(pTHX_ regnode *prog)
            }
 
            PL_op = oop;
-           PL_curpad = ocurpad;
+           PAD_RESTORE_LOCAL(old_comppad);
            PL_curcop = ocurcop;
-           if (logical) {
-               if (logical == 2) {     /* Postponed subexpression. */
+           if (st->logical) {
+               if (st->logical == 2) { /* Postponed subexpression. */
                    regexp *re;
-                   MAGIC *mg = Null(MAGIC*);
+                   MAGIC *mg = NULL;
                    re_cc_state state;
-                   CHECKPOINT cp, lastcp;
-
-                   if(SvROK(ret) || SvRMAGICAL(ret)) {
-                       SV *sv = SvROK(ret) ? SvRV(ret) : ret;
-
-                       if(SvMAGICAL(sv))
-                           mg = mg_find(sv, PERL_MAGIC_qr);
+                    int toggleutf;
+                   register SV *sv;
+
+                   if(SvROK(ret) && SvSMAGICAL(sv = SvRV(ret)))
+                       mg = mg_find(sv, PERL_MAGIC_qr);
+                   else if (SvSMAGICAL(ret)) {
+                       if (SvGMAGICAL(ret))
+                           sv_unmagic(ret, PERL_MAGIC_qr);
+                       else
+                           mg = mg_find(ret, PERL_MAGIC_qr);
                    }
+
                    if (mg) {
                        re = (regexp *)mg->mg_obj;
                        (void)ReREFCNT_inc(re);
                    }
                    else {
                        STRLEN len;
-                       char *t = SvPV(ret, len);
+                       const char * const t = SvPV_const(ret, len);
                        PMOP pm;
-                       char *oprecomp = PL_regprecomp;
-                       I32 osize = PL_regsize;
-                       I32 onpar = PL_regnpar;
+                       char * const oprecomp = PL_regprecomp;
+                       const I32 osize = PL_regsize;
+                       const I32 onpar = PL_regnpar;
 
                        Zero(&pm, 1, PMOP);
-                       re = CALLREGCOMP(aTHX_ t, t + len, &pm);
+                        if (DO_UTF8(ret)) pm.op_pmdynflags |= PMdf_DYN_UTF8;
+                       re = CALLREGCOMP(aTHX_ (char*)t, (char*)t + len, &pm);
                        if (!(SvFLAGS(ret)
-                             & (SVs_TEMP | SVs_PADTMP | SVf_READONLY)))
+                             & (SVs_TEMP | SVs_PADTMP | SVf_READONLY
+                               | SVs_GMG)))
                            sv_magic(ret,(SV*)ReREFCNT_inc(re),
                                        PERL_MAGIC_qr,0,0);
                        PL_regprecomp = oprecomp;
                        PL_regsize = osize;
                        PL_regnpar = onpar;
                    }
-                   DEBUG_r(
+                   DEBUG_EXECUTE_r(
                        PerlIO_printf(Perl_debug_log,
-                                     "Entering embedded `%s%.60s%s%s'\n",
+                                     "Entering embedded \"%s%.60s%s%s\"\n",
                                      PL_colors[0],
                                      re->precomp,
                                      PL_colors[1],
@@ -2860,23 +3342,27 @@ S_regmatch(pTHX_ regnode *prog)
                        );
                    state.node = next;
                    state.prev = PL_reg_call_cc;
-                   state.cc = PL_regcc;
+                   state.cc = st->cc;
                    state.re = PL_reg_re;
 
-                   PL_regcc = 0;
+                   st->cc = 0;
                
-                   cp = regcppush(0);  /* Save *all* the positions. */
-                   REGCP_SET(lastcp);
+                   st->eval.cp = regcppush(0); /* Save *all* the positions. */
+                   REGCP_SET(st->eval.lastcp);
                    cache_re(re);
                    state.ss = PL_savestack_ix;
                    *PL_reglastparen = 0;
                    *PL_reglastcloseparen = 0;
                    PL_reg_call_cc = &state;
                    PL_reginput = locinput;
+                   toggleutf = ((PL_reg_flags & RF_utf8) != 0) ^
+                               ((re->reganch & ROPT_UTF8) != 0);
+                   if (toggleutf) PL_reg_flags ^= RF_utf8;
 
                    /* XXXX This is too dramatic a measure... */
                    PL_reg_maxiter = 0;
 
+                   /* XXX the only recursion left in regmatch() */
                    if (regmatch(re->program + 1)) {
                        /* Even though we succeeded, we need to restore
                           global variables, since we may be wrapped inside
@@ -2884,37 +3370,41 @@ S_regmatch(pTHX_ regnode *prog)
 
                        /* XXXX Do this only if SUSPENDed? */
                        PL_reg_call_cc = state.prev;
-                       PL_regcc = state.cc;
+                       st->cc = state.cc;
                        PL_reg_re = state.re;
                        cache_re(PL_reg_re);
+                       if (toggleutf) PL_reg_flags ^= RF_utf8;
 
                        /* XXXX This is too dramatic a measure... */
                        PL_reg_maxiter = 0;
 
                        /* These are needed even if not SUSPEND. */
                        ReREFCNT_dec(re);
-                       regcpblow(cp);
+                       regcpblow(st->eval.cp);
                        sayYES;
                    }
                    ReREFCNT_dec(re);
-                   REGCP_UNWIND(lastcp);
+                   REGCP_UNWIND(st->eval.lastcp);
                    regcppop();
                    PL_reg_call_cc = state.prev;
-                   PL_regcc = state.cc;
+                   st->cc = state.cc;
                    PL_reg_re = state.re;
                    cache_re(PL_reg_re);
+                   if (toggleutf) PL_reg_flags ^= RF_utf8;
 
                    /* XXXX This is too dramatic a measure... */
                    PL_reg_maxiter = 0;
 
-                   logical = 0;
+                   st->logical = 0;
                    sayNO;
                }
-               sw = SvTRUE(ret);
-               logical = 0;
+               st->sw = SvTRUE(ret);
+               st->logical = 0;
            }
-           else
+           else {
                sv_setsv(save_scalar(PL_replgv), ret);
+               cache_re(oreg);
+           }
            break;
        }
        case OPEN:
@@ -2933,11 +3423,11 @@ S_regmatch(pTHX_ regnode *prog)
            break;
        case GROUPP:
            n = ARG(scan);  /* which paren pair */
-           sw = ((I32)*PL_reglastparen >= n && PL_regendp[n] != -1);
+           st->sw = ((I32)*PL_reglastparen >= n && PL_regendp[n] != -1);
            break;
        case IFTHEN:
            PL_reg_leftiter = PL_reg_maxiter;           /* Void cache */
-           if (sw)
+           if (st->sw)
                next = NEXTOPER(NEXTOPER(scan));
            else {
                next = scan + ARG(scan);
@@ -2946,38 +3436,39 @@ S_regmatch(pTHX_ regnode *prog)
            }
            break;
        case LOGICAL:
-           logical = scan->flags;
+           st->logical = scan->flags;
            break;
 /*******************************************************************
- PL_regcc contains infoblock about the innermost (...)* loop, and
- a pointer to the next outer infoblock.
+ cc points to the regmatch_state associated with the most recent CURLYX.
+ This struct contains info about the innermost (...)* loop (an
+ "infoblock"), and a pointer to the next outer cc.
 
  Here is how Y(A)*Z is processed (if it is compiled into CURLYX/WHILEM):
 
-   1) After matching X, regnode for CURLYX is processed;
+   1) After matching Y, regnode for CURLYX is processed;
 
-   2) This regnode creates infoblock on the stack, and calls
-      regmatch() recursively with the starting point at WHILEM node;
+   2) This regnode populates cc, and calls regmatch() recursively
+      with the starting point at WHILEM node;
 
    3) Each hit of WHILEM node tries to match A and Z (in the order
       depending on the current iteration, min/max of {min,max} and
       greediness).  The information about where are nodes for "A"
-      and "Z" is read from the infoblock, as is info on how many times "A"
+      and "Z" is read from cc, as is info on how many times "A"
       was already matched, and greediness.
 
    4) After A matches, the same WHILEM node is hit again.
 
-   5) Each time WHILEM is hit, PL_regcc is the infoblock created by CURLYX
+   5) Each time WHILEM is hit, cc is the infoblock created by CURLYX
       of the same pair.  Thus when WHILEM tries to match Z, it temporarily
-      resets PL_regcc, since this Y(A)*Z can be a part of some other loop:
+      resets cc, since this Y(A)*Z can be a part of some other loop:
       as in (Y(A)*Z)*.  If Z matches, the automaton will hit the WHILEM node
       of the external loop.
 
- Currently present infoblocks form a tree with a stem formed by PL_curcc
+ Currently present infoblocks form a tree with a stem formed by st->cc
  and whatever it mentions via ->next, and additional attached trees
  corresponding to temporarily unset infoblocks as in "5" above.
 
- In the following picture infoblocks for outer loop of
+ In the following picture, infoblocks for outer loop of
  (Y(A)*?Z)*?T are denoted O, for inner I.  NULL starting block
  is denoted by x.  The matched string is YAAZYAZT.  Temporarily postponed
  infoblocks are drawn below the "reset" infoblock.
@@ -3023,35 +3514,40 @@ S_regmatch(pTHX_ regnode *prog)
                                O
                                I,I
  *******************************************************************/
+
        case CURLYX: {
-               CURCUR cc;
-               CHECKPOINT cp = PL_savestack_ix;
                /* No need to save/restore up to this paren */
                I32 parenfloor = scan->flags;
 
                if (OP(PREVOPER(next)) == NOTHING) /* LONGJMP */
                    next += ARG(next);
-               cc.oldcc = PL_regcc;
-               PL_regcc = &cc;
                /* XXXX Probably it is better to teach regpush to support
                   parenfloor > PL_regsize... */
                if (parenfloor > (I32)*PL_reglastparen)
                    parenfloor = *PL_reglastparen; /* Pessimization... */
-               cc.parenfloor = parenfloor;
-               cc.cur = -1;
-               cc.min = ARG1(scan);
-               cc.max  = ARG2(scan);
-               cc.scan = NEXTOPER(scan) + EXTRA_STEP_2ARGS;
-               cc.next = next;
-               cc.minmod = minmod;
-               cc.lastloc = 0;
+
+               st->curlyx.cp = PL_savestack_ix;
+               st->curlyx.outercc = st->cc;
+               st->cc = st;
+               /* these fields contain the state of the current curly.
+                * they are accessed by subsequent WHILEMs;
+                * cur and lastloc are also updated by WHILEM */
+               st->curlyx.parenfloor = parenfloor;
+               st->curlyx.cur = -1; /* this will be updated by WHILEM */
+               st->curlyx.min = ARG1(scan);
+               st->curlyx.max  = ARG2(scan);
+               st->curlyx.scan = NEXTOPER(scan) + EXTRA_STEP_2ARGS;
+               st->curlyx.lastloc = 0;
+               /* st->next and st->minmod are also read by WHILEM */
+
                PL_reginput = locinput;
-               n = regmatch(PREVOPER(next));   /* start on the WHILEM */
-               regcpblow(cp);
-               PL_regcc = cc.oldcc;
-               saySAME(n);
+               REGMATCH(PREVOPER(next), CURLYX); /* start on the WHILEM */
+               /*** all unsaved local vars undefined at this point */
+               regcpblow(st->curlyx.cp);
+               st->cc = st->curlyx.outercc;
+               saySAME(result);
            }
-           /* NOT REACHED */
+           /* NOTREACHED */
        case WHILEM: {
                /*
                 * This is really hard to understand, because after we match
@@ -3062,49 +3558,54 @@ S_regmatch(pTHX_ regnode *prog)
                 * that we can try again after backing off.
                 */
 
-               CHECKPOINT cp, lastcp;
-               CURCUR* cc = PL_regcc;
-               char *lastloc = cc->lastloc; /* Detection of 0-len. */
+               st->whilem.lastloc = st->cc->curlyx.lastloc; /* Detection of 0-len. */
+               st->whilem.cache_offset = 0;
+               st->whilem.cache_bit = 0;
                
-               n = cc->cur + 1;        /* how many we know we matched */
+               n = st->cc->curlyx.cur + 1; /* how many we know we matched */
                PL_reginput = locinput;
 
-               DEBUG_r(
+               DEBUG_EXECUTE_r(
                    PerlIO_printf(Perl_debug_log,
                                  "%*s  %ld out of %ld..%ld  cc=%"UVxf"\n",
                                  REPORT_CODE_OFF+PL_regindent*2, "",
-                                 (long)n, (long)cc->min,
-                                 (long)cc->max, PTR2UV(cc))
+                                 (long)n, (long)st->cc->curlyx.min,
+                                 (long)st->cc->curlyx.max, PTR2UV(st->cc))
                    );
 
                /* If degenerate scan matches "", assume scan done. */
 
-               if (locinput == cc->lastloc && n >= cc->min) {
-                   PL_regcc = cc->oldcc;
-                   if (PL_regcc)
-                       ln = PL_regcc->cur;
-                   DEBUG_r(
+               if (locinput == st->cc->curlyx.lastloc && n >= st->cc->curlyx.min) {
+                   st->whilem.savecc = st->cc;
+                   st->cc = st->cc->curlyx.outercc;
+                   if (st->cc)
+                       st->ln = st->cc->curlyx.cur;
+                   DEBUG_EXECUTE_r(
                        PerlIO_printf(Perl_debug_log,
                           "%*s  empty match detected, try continuation...\n",
                           REPORT_CODE_OFF+PL_regindent*2, "")
                        );
-                   if (regmatch(cc->next))
+                   REGMATCH(st->whilem.savecc->next, WHILEM1);
+                   /*** all unsaved local vars undefined at this point */
+                   st->cc = st->whilem.savecc;
+                   if (result)
                        sayYES;
-                   if (PL_regcc)
-                       PL_regcc->cur = ln;
-                   PL_regcc = cc;
+                   if (st->cc->curlyx.outercc)
+                       st->cc->curlyx.outercc->curlyx.cur = st->ln;
                    sayNO;
                }
 
                /* First just match a string of min scans. */
 
-               if (n < cc->min) {
-                   cc->cur = n;
-                   cc->lastloc = locinput;
-                   if (regmatch(cc->scan))
+               if (n < st->cc->curlyx.min) {
+                   st->cc->curlyx.cur = n;
+                   st->cc->curlyx.lastloc = locinput;
+                   REGMATCH(st->cc->curlyx.scan, WHILEM2);
+                   /*** all unsaved local vars undefined at this point */
+                   if (result)
                        sayYES;
-                   cc->cur = n - 1;
-                   cc->lastloc = lastloc;
+                   st->cc->curlyx.cur = n - 1;
+                   st->cc->curlyx.lastloc = st->whilem.lastloc;
                    sayNO;
                }
 
@@ -3117,7 +3618,7 @@ S_regmatch(pTHX_ regnode *prog)
                    PL_reg_leftiter = PL_reg_maxiter;
                }
                if (PL_reg_leftiter-- == 0) {
-                   I32 size = (PL_reg_maxiter + 7)/8;
+                   const I32 size = (PL_reg_maxiter + 7 + POSCACHE_START)/8;
                    if (PL_reg_poscache) {
                        if ((I32)PL_reg_poscache_size < size) {
                            Renew(PL_reg_poscache, size, char);
@@ -3127,51 +3628,60 @@ S_regmatch(pTHX_ regnode *prog)
                    }
                    else {
                        PL_reg_poscache_size = size;
-                       Newz(29, PL_reg_poscache, size, char);
+                       Newxz(PL_reg_poscache, size, char);
                    }
-                   DEBUG_r(
+                   DEBUG_EXECUTE_r(
                        PerlIO_printf(Perl_debug_log,
              "%sDetected a super-linear match, switching on caching%s...\n",
                                      PL_colors[4], PL_colors[5])
                        );
                }
                if (PL_reg_leftiter < 0) {
-                   I32 o = locinput - PL_bostr, b;
-
-                   o = (scan->flags & 0xf) - 1 + o * (scan->flags>>4);
-                   b = o % 8;
-                   o /= 8;
-                   if (PL_reg_poscache[o] & (1<<b)) {
-                   DEBUG_r(
+                   st->whilem.cache_offset = locinput - PL_bostr;
+
+                   st->whilem.cache_offset = (scan->flags & 0xf) - 1 + POSCACHE_START
+                           + st->whilem.cache_offset * (scan->flags>>4);
+                   st->whilem.cache_bit = st->whilem.cache_offset % 8;
+                   st->whilem.cache_offset /= 8;
+                   if (PL_reg_poscache[st->whilem.cache_offset] & (1<<st->whilem.cache_bit)) {
+                   DEBUG_EXECUTE_r(
                        PerlIO_printf(Perl_debug_log,
                                      "%*s  already tried at this position...\n",
                                      REPORT_CODE_OFF+PL_regindent*2, "")
                        );
-                       sayNO_SILENT;
+                       if (PL_reg_poscache[0] & (1<<POSCACHE_SUCCESS))
+                           /* cache records success */
+                           sayYES;
+                       else
+                           /* cache records failure */
+                           sayNO_SILENT;
                    }
-                   PL_reg_poscache[o] |= (1<<b);
+                   PL_reg_poscache[st->whilem.cache_offset] |= (1<<st->whilem.cache_bit);
                }
                }
 
                /* Prefer next over scan for minimal matching. */
 
-               if (cc->minmod) {
-                   PL_regcc = cc->oldcc;
-                   if (PL_regcc)
-                       ln = PL_regcc->cur;
-                   cp = regcppush(cc->parenfloor);
-                   REGCP_SET(lastcp);
-                   if (regmatch(cc->next)) {
-                       regcpblow(cp);
-                       sayYES; /* All done. */
+               if (st->cc->minmod) {
+                   st->whilem.savecc = st->cc;
+                   st->cc = st->cc->curlyx.outercc;
+                   if (st->cc)
+                       st->ln = st->cc->curlyx.cur;
+                   st->whilem.cp = regcppush(st->whilem.savecc->curlyx.parenfloor);
+                   REGCP_SET(st->whilem.lastcp);
+                   REGMATCH(st->whilem.savecc->next, WHILEM3);
+                   /*** all unsaved local vars undefined at this point */
+                   st->cc = st->whilem.savecc;
+                   if (result) {
+                       regcpblow(st->whilem.cp);
+                       CACHEsayYES;    /* All done. */
                    }
-                   REGCP_UNWIND(lastcp);
+                   REGCP_UNWIND(st->whilem.lastcp);
                    regcppop();
-                   if (PL_regcc)
-                       PL_regcc->cur = ln;
-                   PL_regcc = cc;
+                   if (st->cc->curlyx.outercc)
+                       st->cc->curlyx.outercc->curlyx.cur = st->ln;
 
-                   if (n >= cc->max) { /* Maximum greed exceeded? */
+                   if (n >= st->cc->curlyx.max) { /* Maximum greed exceeded? */
                        if (ckWARN(WARN_REGEXP) && n >= REG_INFTY
                            && !(PL_reg_flags & RF_warned)) {
                            PL_reg_flags |= RF_warned;
@@ -3179,46 +3689,50 @@ S_regmatch(pTHX_ regnode *prog)
                                 "Complex regular subexpression recursion",
                                 REG_INFTY - 1);
                        }
-                       sayNO;
+                       CACHEsayNO;
                    }
 
-                   DEBUG_r(
+                   DEBUG_EXECUTE_r(
                        PerlIO_printf(Perl_debug_log,
                                      "%*s  trying longer...\n",
                                      REPORT_CODE_OFF+PL_regindent*2, "")
                        );
                    /* Try scanning more and see if it helps. */
                    PL_reginput = locinput;
-                   cc->cur = n;
-                   cc->lastloc = locinput;
-                   cp = regcppush(cc->parenfloor);
-                   REGCP_SET(lastcp);
-                   if (regmatch(cc->scan)) {
-                       regcpblow(cp);
-                       sayYES;
+                   st->cc->curlyx.cur = n;
+                   st->cc->curlyx.lastloc = locinput;
+                   st->whilem.cp = regcppush(st->cc->curlyx.parenfloor);
+                   REGCP_SET(st->whilem.lastcp);
+                   REGMATCH(st->cc->curlyx.scan, WHILEM4);
+                   /*** all unsaved local vars undefined at this point */
+                   if (result) {
+                       regcpblow(st->whilem.cp);
+                       CACHEsayYES;
                    }
-                   REGCP_UNWIND(lastcp);
+                   REGCP_UNWIND(st->whilem.lastcp);
                    regcppop();
-                   cc->cur = n - 1;
-                   cc->lastloc = lastloc;
-                   sayNO;
+                   st->cc->curlyx.cur = n - 1;
+                   st->cc->curlyx.lastloc = st->whilem.lastloc;
+                   CACHEsayNO;
                }
 
                /* Prefer scan over next for maximal matching. */
 
-               if (n < cc->max) {      /* More greed allowed? */
-                   cp = regcppush(cc->parenfloor);
-                   cc->cur = n;
-                   cc->lastloc = locinput;
-                   REGCP_SET(lastcp);
-                   if (regmatch(cc->scan)) {
-                       regcpblow(cp);
-                       sayYES;
+               if (n < st->cc->curlyx.max) {   /* More greed allowed? */
+                   st->whilem.cp = regcppush(st->cc->curlyx.parenfloor);
+                   st->cc->curlyx.cur = n;
+                   st->cc->curlyx.lastloc = locinput;
+                   REGCP_SET(st->whilem.lastcp);
+                   REGMATCH(st->cc->curlyx.scan, WHILEM5);
+                   /*** all unsaved local vars undefined at this point */
+                   if (result) {
+                       regcpblow(st->whilem.cp);
+                       CACHEsayYES;
                    }
-                   REGCP_UNWIND(lastcp);
+                   REGCP_UNWIND(st->whilem.lastcp);
                    regcppop();         /* Restore some previous $<digit>s? */
                    PL_reginput = locinput;
-                   DEBUG_r(
+                   DEBUG_EXECUTE_r(
                        PerlIO_printf(Perl_debug_log,
                                      "%*s  failed, try continuation...\n",
                                      REPORT_CODE_OFF+PL_regindent*2, "")
@@ -3233,19 +3747,22 @@ S_regmatch(pTHX_ regnode *prog)
                }
 
                /* Failed deeper matches of scan, so see if this one works. */
-               PL_regcc = cc->oldcc;
-               if (PL_regcc)
-                   ln = PL_regcc->cur;
-               if (regmatch(cc->next))
-                   sayYES;
-               if (PL_regcc)
-                   PL_regcc->cur = ln;
-               PL_regcc = cc;
-               cc->cur = n - 1;
-               cc->lastloc = lastloc;
-               sayNO;
+               st->whilem.savecc = st->cc;
+               st->cc = st->cc->curlyx.outercc;
+               if (st->cc)
+                   st->ln = st->cc->curlyx.cur;
+               REGMATCH(st->whilem.savecc->next, WHILEM6);
+               /*** all unsaved local vars undefined at this point */
+               st->cc = st->whilem.savecc;
+               if (result)
+                   CACHEsayYES;
+               if (st->cc->curlyx.outercc)
+                   st->cc->curlyx.outercc->curlyx.cur = st->ln;
+               st->cc->curlyx.cur = n - 1;
+               st->cc->curlyx.lastloc = st->whilem.lastloc;
+               CACHEsayNO;
            }
-           /* NOT REACHED */
+           /* NOTREACHED */
        case BRANCHJ:
            next = scan + ARG(scan);
            if (next == scan)
@@ -3256,20 +3773,19 @@ S_regmatch(pTHX_ regnode *prog)
            inner = NEXTOPER(scan);
          do_branch:
            {
-               c1 = OP(scan);
-               if (OP(next) != c1)     /* No choice. */
+               I32 type;
+               type = OP(scan);
+               if (OP(next) != type)   /* No choice. */
                    next = inner;       /* Avoid recursion. */
                else {
-                   I32 lastparen = *PL_reglastparen;
-                   I32 unwind1;
-                   re_unwind_branch_t *uw;
-
+                   const I32 lastparen = *PL_reglastparen;
                    /* Put unwinding data on stack */
-                   unwind1 = SSNEWt(1,re_unwind_branch_t);
-                   uw = SSPTRt(unwind1,re_unwind_branch_t);
-                   uw->prev = unwind;
-                   unwind = unwind1;
-                   uw->type = ((c1 == BRANCH)
+                   const I32 unwind1 = SSNEWt(1,re_unwind_branch_t);
+                   re_unwind_branch_t * const uw = SSPTRt(unwind1,re_unwind_branch_t);
+
+                   uw->prev = st->unwind;
+                   st->unwind = unwind1;
+                   uw->type = ((type == BRANCH)
                                ? RE_UNWIND_BRANCH
                                : RE_UNWIND_BRANCHJ);
                    uw->lastparen = lastparen;
@@ -3288,102 +3804,113 @@ S_regmatch(pTHX_ regnode *prog)
            }
            break;
        case MINMOD:
-           minmod = 1;
+           st->minmod = 1;
            break;
        case CURLYM:
        {
-           I32 l = 0;
-           CHECKPOINT lastcp;
+           st->curlym.l = st->curlym.matches = 0;
        
            /* We suppose that the next guy does not need
-              backtracking: in particular, it is of constant length,
+              backtracking: in particular, it is of constant non-zero length,
               and has no parenths to influence future backrefs. */
-           ln = ARG1(scan);  /* min to match */
+           st->ln = ARG1(scan);  /* min to match */
            n  = ARG2(scan);  /* max to match */
-           paren = scan->flags;
-           if (paren) {
-               if (paren > PL_regsize)
-                   PL_regsize = paren;
-               if (paren > (I32)*PL_reglastparen)
-                   *PL_reglastparen = paren;
+           st->curlym.paren = scan->flags;
+           if (st->curlym.paren) {
+               if (st->curlym.paren > PL_regsize)
+                   PL_regsize = st->curlym.paren;
+               if (st->curlym.paren > (I32)*PL_reglastparen)
+                   *PL_reglastparen = st->curlym.paren;
            }
            scan = NEXTOPER(scan) + NODE_STEP_REGNODE;
-           if (paren)
+           if (st->curlym.paren)
                scan += NEXT_OFF(scan); /* Skip former OPEN. */
            PL_reginput = locinput;
-           if (minmod) {
-               minmod = 0;
-               if (ln && regrepeat_hard(scan, ln, &l) < ln)
+           st->curlym.maxwanted = st->minmod ? st->ln : n;
+           if (st->curlym.maxwanted) {
+               while (PL_reginput < PL_regeol && st->curlym.matches < st->curlym.maxwanted) {
+                   REGMATCH(scan, CURLYM1);
+                   /*** all unsaved local vars undefined at this point */
+                   if (!result)
+                       break;
+                   /* on first match, determine length, curlym.l */
+                   if (!st->curlym.matches++) {
+                       if (PL_reg_match_utf8) {
+                           char *s = locinput;
+                           while (s < PL_reginput) {
+                               st->curlym.l++;
+                               s += UTF8SKIP(s);
+                           }
+                       }
+                       else {
+                           st->curlym.l = PL_reginput - locinput;
+                       }
+                       if (st->curlym.l == 0) {
+                           st->curlym.matches = st->curlym.maxwanted;
+                           break;
+                       }
+                   }
+                   locinput = PL_reginput;
+               }
+           }
+
+           PL_reginput = locinput;
+
+           if (st->minmod) {
+               st->minmod = 0;
+               if (st->ln && st->curlym.matches < st->ln)
                    sayNO;
-               /* if we matched something zero-length we don't need to
-                  backtrack - capturing parens are already defined, so
-                  the caveat in the maximal case doesn't apply
-
-                  XXXX if ln == 0, we can redo this check first time
-                  through the following loop
-               */
-               if (ln && l == 0)
-                   n = ln;     /* don't backtrack */
-               locinput = PL_reginput;
                if (HAS_TEXT(next) || JUMPABLE(next)) {
                    regnode *text_node = next;
 
                    if (! HAS_TEXT(text_node)) FIND_NEXT_IMPT(text_node);
 
-                   if (! HAS_TEXT(text_node)) c1 = c2 = -1000;
+                   if (! HAS_TEXT(text_node)) st->curlym.c1 = st->curlym.c2 = -1000;
                    else {
                        if (PL_regkind[(U8)OP(text_node)] == REF) {
-                           I32 n, ln;
-                           n = ARG(text_node);  /* which paren pair */
-                           ln = PL_regstartp[n];
-                           /* assume yes if we haven't seen CLOSEn */
-                           if (
-                               (I32)*PL_reglastparen < n ||
-                               ln == -1 ||
-                               ln == PL_regendp[n]
-                           ) {
-                               c1 = c2 = -1000;
-                               goto assume_ok_MM;
-                           }
-                           c1 = *(PL_bostr + ln);
+                           st->curlym.c1 = st->curlym.c2 = -1000;
+                           goto assume_ok_MM;
                        }
-                       else { c1 = (U8)*STRING(text_node); }
+                       else { st->curlym.c1 = (U8)*STRING(text_node); }
                        if (OP(text_node) == EXACTF || OP(text_node) == REFF)
-                           c2 = PL_fold[c1];
+                           st->curlym.c2 = PL_fold[st->curlym.c1];
                        else if (OP(text_node) == EXACTFL || OP(text_node) == REFFL)
-                           c2 = PL_fold_locale[c1];
+                           st->curlym.c2 = PL_fold_locale[st->curlym.c1];
                        else
-                           c2 = c1;
+                           st->curlym.c2 = st->curlym.c1;
                    }
                }
                else
-                   c1 = c2 = -1000;
+                   st->curlym.c1 = st->curlym.c2 = -1000;
            assume_ok_MM:
-               REGCP_SET(lastcp);
-               /* This may be improved if l == 0.  */
-               while (n >= ln || (n == REG_INFTY && ln > 0 && l)) { /* ln overflow ? */
+               REGCP_SET(st->curlym.lastcp);
+               while (n >= st->ln || (n == REG_INFTY && st->ln > 0)) { /* ln overflow ? */
                    /* If it could work, try it. */
-                   if (c1 == -1000 ||
-                       UCHARAT(PL_reginput) == c1 ||
-                       UCHARAT(PL_reginput) == c2)
+                   if (st->curlym.c1 == -1000 ||
+                       UCHARAT(PL_reginput) == st->curlym.c1 ||
+                       UCHARAT(PL_reginput) == st->curlym.c2)
                    {
-                       if (paren) {
-                           if (ln) {
-                               PL_regstartp[paren] =
-                                   HOPc(PL_reginput, -l) - PL_bostr;
-                               PL_regendp[paren] = PL_reginput - PL_bostr;
+                       if (st->curlym.paren) {
+                           if (st->ln) {
+                               PL_regstartp[st->curlym.paren] =
+                                   HOPc(PL_reginput, -st->curlym.l) - PL_bostr;
+                               PL_regendp[st->curlym.paren] = PL_reginput - PL_bostr;
                            }
                            else
-                               PL_regendp[paren] = -1;
+                               PL_regendp[st->curlym.paren] = -1;
                        }
-                       if (regmatch(next))
+                       REGMATCH(next, CURLYM2);
+                       /*** all unsaved local vars undefined at this point */
+                       if (result)
                            sayYES;
-                       REGCP_UNWIND(lastcp);
+                       REGCP_UNWIND(st->curlym.lastcp);
                    }
                    /* Couldn't or didn't -- move forward. */
                    PL_reginput = locinput;
-                   if (regrepeat_hard(scan, 1, &l)) {
-                       ln++;
+                   REGMATCH(scan, CURLYM3);
+                   /*** all unsaved local vars undefined at this point */
+                   if (result) {
+                       st->ln++;
                        locinput = PL_reginput;
                    }
                    else
@@ -3391,118 +3918,103 @@ S_regmatch(pTHX_ regnode *prog)
                }
            }
            else {
-               n = regrepeat_hard(scan, n, &l);
-               /* if we matched something zero-length we don't need to
-                  backtrack, unless the minimum count is zero and we
-                  are capturing the result - in that case the capture
-                  being defined or not may affect later execution
-               */
-               if (n != 0 && l == 0 && !(paren && ln == 0))
-                   ln = n;     /* don't backtrack */
-               locinput = PL_reginput;
-               DEBUG_r(
+               DEBUG_EXECUTE_r(
                    PerlIO_printf(Perl_debug_log,
-                                 "%*s  matched %"IVdf" times, len=%"IVdf"...\n",
-                                 (int)(REPORT_CODE_OFF+PL_regindent*2), "",
-                                 (IV) n, (IV)l)
+                             "%*s  matched %"IVdf" times, len=%"IVdf"...\n",
+                             (int)(REPORT_CODE_OFF+PL_regindent*2), "",
+                             (IV) st->curlym.matches, (IV)st->curlym.l)
                    );
-               if (n >= ln) {
+               if (st->curlym.matches >= st->ln) {
                    if (HAS_TEXT(next) || JUMPABLE(next)) {
                        regnode *text_node = next;
 
                        if (! HAS_TEXT(text_node)) FIND_NEXT_IMPT(text_node);
 
-                       if (! HAS_TEXT(text_node)) c1 = c2 = -1000;
+                       if (! HAS_TEXT(text_node)) st->curlym.c1 = st->curlym.c2 = -1000;
                        else {
                            if (PL_regkind[(U8)OP(text_node)] == REF) {
-                               I32 n, ln;
-                               n = ARG(text_node);  /* which paren pair */
-                               ln = PL_regstartp[n];
-                               /* assume yes if we haven't seen CLOSEn */
-                               if (
-                                   (I32)*PL_reglastparen < n ||
-                                   ln == -1 ||
-                                   ln == PL_regendp[n]
-                               ) {
-                                   c1 = c2 = -1000;
-                                   goto assume_ok_REG;
-                               }
-                               c1 = *(PL_bostr + ln);
+                               st->curlym.c1 = st->curlym.c2 = -1000;
+                               goto assume_ok_REG;
                            }
-                           else { c1 = (U8)*STRING(text_node); }
+                           else { st->curlym.c1 = (U8)*STRING(text_node); }
 
                            if (OP(text_node) == EXACTF || OP(text_node) == REFF)
-                               c2 = PL_fold[c1];
+                               st->curlym.c2 = PL_fold[st->curlym.c1];
                            else if (OP(text_node) == EXACTFL || OP(text_node) == REFFL)
-                               c2 = PL_fold_locale[c1];
+                               st->curlym.c2 = PL_fold_locale[st->curlym.c1];
                            else
-                               c2 = c1;
+                               st->curlym.c2 = st->curlym.c1;
                        }
                    }
                    else
-                       c1 = c2 = -1000;
+                       st->curlym.c1 = st->curlym.c2 = -1000;
                }
            assume_ok_REG:
-               REGCP_SET(lastcp);
-               while (n >= ln) {
+               REGCP_SET(st->curlym.lastcp);
+               while (st->curlym.matches >= st->ln) {
                    /* If it could work, try it. */
-                   if (c1 == -1000 ||
-                       UCHARAT(PL_reginput) == c1 ||
-                       UCHARAT(PL_reginput) == c2)
+                   if (st->curlym.c1 == -1000 ||
+                       UCHARAT(PL_reginput) == st->curlym.c1 ||
+                       UCHARAT(PL_reginput) == st->curlym.c2)
                    {
-                       DEBUG_r(
-                               PerlIO_printf(Perl_debug_log,
-                                             "%*s  trying tail with n=%"IVdf"...\n",
-                                             (int)(REPORT_CODE_OFF+PL_regindent*2), "", (IV)n)
+                       DEBUG_EXECUTE_r(
+                           PerlIO_printf(Perl_debug_log,
+                               "%*s  trying tail with matches=%"IVdf"...\n",
+                               (int)(REPORT_CODE_OFF+PL_regindent*2),
+                               "", (IV)st->curlym.matches)
                            );
-                       if (paren) {
-                           if (n) {
-                               PL_regstartp[paren] = HOPc(PL_reginput, -l) - PL_bostr;
-                               PL_regendp[paren] = PL_reginput - PL_bostr;
+                       if (st->curlym.paren) {
+                           if (st->curlym.matches) {
+                               PL_regstartp[st->curlym.paren]
+                                   = HOPc(PL_reginput, -st->curlym.l) - PL_bostr;
+                               PL_regendp[st->curlym.paren] = PL_reginput - PL_bostr;
                            }
                            else
-                               PL_regendp[paren] = -1;
+                               PL_regendp[st->curlym.paren] = -1;
                        }
-                       if (regmatch(next))
+                       REGMATCH(next, CURLYM4);
+                       /*** all unsaved local vars undefined at this point */
+                       if (result)
                            sayYES;
-                       REGCP_UNWIND(lastcp);
+                       REGCP_UNWIND(st->curlym.lastcp);
                    }
                    /* Couldn't or didn't -- back up. */
-                   n--;
-                   locinput = HOPc(locinput, -l);
+                   st->curlym.matches--;
+                   locinput = HOPc(locinput, -st->curlym.l);
                    PL_reginput = locinput;
                }
            }
            sayNO;
+           /* NOTREACHED */
            break;
        }
        case CURLYN:
-           paren = scan->flags;        /* Which paren to set */
-           if (paren > PL_regsize)
-               PL_regsize = paren;
-           if (paren > (I32)*PL_reglastparen)
-               *PL_reglastparen = paren;
-           ln = ARG1(scan);  /* min to match */
+           st->plus.paren = scan->flags;       /* Which paren to set */
+           if (st->plus.paren > PL_regsize)
+               PL_regsize = st->plus.paren;
+           if (st->plus.paren > (I32)*PL_reglastparen)
+               *PL_reglastparen = st->plus.paren;
+           st->ln = ARG1(scan);  /* min to match */
            n  = ARG2(scan);  /* max to match */
             scan = regnext(NEXTOPER(scan) + NODE_STEP_REGNODE);
            goto repeat;
        case CURLY:
-           paren = 0;
-           ln = ARG1(scan);  /* min to match */
+           st->plus.paren = 0;
+           st->ln = ARG1(scan);  /* min to match */
            n  = ARG2(scan);  /* max to match */
            scan = NEXTOPER(scan) + NODE_STEP_REGNODE;
            goto repeat;
        case STAR:
-           ln = 0;
+           st->ln = 0;
            n = REG_INFTY;
            scan = NEXTOPER(scan);
-           paren = 0;
+           st->plus.paren = 0;
            goto repeat;
        case PLUS:
-           ln = 1;
+           st->ln = 1;
            n = REG_INFTY;
            scan = NEXTOPER(scan);
-           paren = 0;
+           st->plus.paren = 0;
          repeat:
            /*
            * Lookahead to avoid useless match attempts
@@ -3521,181 +4033,166 @@ S_regmatch(pTHX_ regnode *prog)
 
                if (! HAS_TEXT(text_node)) FIND_NEXT_IMPT(text_node);
 
-               if (! HAS_TEXT(text_node)) c1 = c2 = -1000;
+               if (! HAS_TEXT(text_node)) st->plus.c1 = st->plus.c2 = -1000;
                else {
                    if (PL_regkind[(U8)OP(text_node)] == REF) {
-                       I32 n, ln;
-                       n = ARG(text_node);  /* which paren pair */
-                       ln = PL_regstartp[n];
-                       /* assume yes if we haven't seen CLOSEn */
-                       if (
-                           (I32)*PL_reglastparen < n ||
-                           ln == -1 ||
-                           ln == PL_regendp[n]
-                       ) {
-                           c1 = c2 = -1000;
-                           goto assume_ok_easy;
-                       }
-                       s = (U8*)PL_bostr + ln;
+                       st->plus.c1 = st->plus.c2 = -1000;
+                       goto assume_ok_easy;
                    }
                    else { s = (U8*)STRING(text_node); }
 
                    if (!UTF) {
-                       c2 = c1 = *s;
+                       st->plus.c2 = st->plus.c1 = *s;
                        if (OP(text_node) == EXACTF || OP(text_node) == REFF)
-                           c2 = PL_fold[c1];
+                           st->plus.c2 = PL_fold[st->plus.c1];
                        else if (OP(text_node) == EXACTFL || OP(text_node) == REFFL)
-                           c2 = PL_fold_locale[c1];
+                           st->plus.c2 = PL_fold_locale[st->plus.c1];
                    }
                    else { /* UTF */
                        if (OP(text_node) == EXACTF || OP(text_node) == REFF) {
                             STRLEN ulen1, ulen2;
-                            U8 tmpbuf1[UTF8_MAXLEN_UCLC+1];
-                            U8 tmpbuf2[UTF8_MAXLEN_UCLC+1];
+                            U8 tmpbuf1[UTF8_MAXBYTES_CASE+1];
+                            U8 tmpbuf2[UTF8_MAXBYTES_CASE+1];
 
                             to_utf8_lower((U8*)s, tmpbuf1, &ulen1);
                             to_utf8_upper((U8*)s, tmpbuf2, &ulen2);
 
-                            c1 = utf8n_to_uvuni(tmpbuf1, UTF8_MAXLEN, 0,
-                                                ckWARN(WARN_UTF8) ?
-                                                0 : UTF8_ALLOW_ANY);
-                            c2 = utf8n_to_uvuni(tmpbuf2, UTF8_MAXLEN, 0,
-                                                ckWARN(WARN_UTF8) ?
-                                                0 : UTF8_ALLOW_ANY);
+                            st->plus.c1 = utf8n_to_uvuni(tmpbuf1, UTF8_MAXBYTES, 0,
+                                                uniflags);
+                            st->plus.c2 = utf8n_to_uvuni(tmpbuf2, UTF8_MAXBYTES, 0,
+                                                uniflags);
                        }
                        else {
-                           c2 = c1 = utf8n_to_uvchr(s, UTF8_MAXLEN, 0,
-                                                    ckWARN(WARN_UTF8) ?
-                                                    0 : UTF8_ALLOW_ANY);
+                           st->plus.c2 = st->plus.c1 = utf8n_to_uvchr(s, UTF8_MAXBYTES, 0,
+                                                    uniflags);
                        }
                    }
                }
            }
            else
-               c1 = c2 = -1000;
+               st->plus.c1 = st->plus.c2 = -1000;
        assume_ok_easy:
            PL_reginput = locinput;
-           if (minmod) {
-               CHECKPOINT lastcp;
-               minmod = 0;
-               if (ln && regrepeat(scan, ln) < ln)
+           if (st->minmod) {
+               st->minmod = 0;
+               if (st->ln && regrepeat(scan, st->ln) < st->ln)
                    sayNO;
                locinput = PL_reginput;
-               REGCP_SET(lastcp);
-               if (c1 != -1000) {
-                   char *e; /* Should not check after this */
-                   char *old = locinput;
-                   int count = 0;
+               REGCP_SET(st->plus.lastcp);
+               if (st->plus.c1 != -1000) {
+                   st->plus.old = locinput;
+                   st->plus.count = 0;
 
                    if  (n == REG_INFTY) {
-                       e = PL_regeol - 1;
+                       st->plus.e = PL_regeol - 1;
                        if (do_utf8)
-                           while (UTF8_IS_CONTINUATION(*(U8*)e))
-                               e--;
+                           while (UTF8_IS_CONTINUATION(*(U8*)st->plus.e))
+                               st->plus.e--;
                    }
                    else if (do_utf8) {
-                       int m = n - ln;
-                       for (e = locinput;
-                            m >0 && e + UTF8SKIP(e) <= PL_regeol; m--)
-                           e += UTF8SKIP(e);
+                       int m = n - st->ln;
+                       for (st->plus.e = locinput;
+                            m >0 && st->plus.e + UTF8SKIP(st->plus.e) <= PL_regeol; m--)
+                           st->plus.e += UTF8SKIP(st->plus.e);
                    }
                    else {
-                       e = locinput + n - ln;
-                       if (e >= PL_regeol)
-                           e = PL_regeol - 1;
+                       st->plus.e = locinput + n - st->ln;
+                       if (st->plus.e >= PL_regeol)
+                           st->plus.e = PL_regeol - 1;
                    }
                    while (1) {
                        /* Find place 'next' could work */
                        if (!do_utf8) {
-                           if (c1 == c2) {
-                               while (locinput <= e &&
-                                      UCHARAT(locinput) != c1)
+                           if (st->plus.c1 == st->plus.c2) {
+                               while (locinput <= st->plus.e &&
+                                      UCHARAT(locinput) != st->plus.c1)
                                    locinput++;
                            } else {
-                               while (locinput <= e
-                                      && UCHARAT(locinput) != c1
-                                      && UCHARAT(locinput) != c2)
+                               while (locinput <= st->plus.e
+                                      && UCHARAT(locinput) != st->plus.c1
+                                      && UCHARAT(locinput) != st->plus.c2)
                                    locinput++;
                            }
-                           count = locinput - old;
+                           st->plus.count = locinput - st->plus.old;
                        }
                        else {
-                           STRLEN len;
-                           if (c1 == c2) {
+                           if (st->plus.c1 == st->plus.c2) {
+                               STRLEN len;
                                /* count initialised to
                                 * utf8_distance(old, locinput) */
-                               while (locinput <= e &&
+                               while (locinput <= st->plus.e &&
                                       utf8n_to_uvchr((U8*)locinput,
-                                                     UTF8_MAXLEN, &len,
-                                                     ckWARN(WARN_UTF8) ?
-                                                     0 : UTF8_ALLOW_ANY) != (UV)c1) {
+                                                     UTF8_MAXBYTES, &len,
+                                                     uniflags) != (UV)st->plus.c1) {
                                    locinput += len;
-                                   count++;
+                                   st->plus.count++;
                                }
                            } else {
+                               STRLEN len;
                                /* count initialised to
                                 * utf8_distance(old, locinput) */
-                               while (locinput <= e) {
+                               while (locinput <= st->plus.e) {
                                    UV c = utf8n_to_uvchr((U8*)locinput,
-                                                         UTF8_MAXLEN, &len,
-                                                         ckWARN(WARN_UTF8) ?
-                                                         0 : UTF8_ALLOW_ANY);
-                                   if (c == (UV)c1 || c == (UV)c2)
+                                                         UTF8_MAXBYTES, &len,
+                                                         uniflags);
+                                   if (c == (UV)st->plus.c1 || c == (UV)st->plus.c2)
                                        break;
                                    locinput += len;
-                                   count++;
+                                   st->plus.count++;
                                }
                            }
                        }
-                       if (locinput > e)
+                       if (locinput > st->plus.e)
                            sayNO;
                        /* PL_reginput == old now */
-                       if (locinput != old) {
-                           ln = 1;     /* Did some */
-                           if (regrepeat(scan, count) < count)
+                       if (locinput != st->plus.old) {
+                           st->ln = 1; /* Did some */
+                           if (regrepeat(scan, st->plus.count) < st->plus.count)
                                sayNO;
                        }
                        /* PL_reginput == locinput now */
-                       TRYPAREN(paren, ln, locinput);
+                       TRYPAREN(st->plus.paren, st->ln, locinput, PLUS1);
+                       /*** all unsaved local vars undefined at this point */
                        PL_reginput = locinput; /* Could be reset... */
-                       REGCP_UNWIND(lastcp);
+                       REGCP_UNWIND(st->plus.lastcp);
                        /* Couldn't or didn't -- move forward. */
-                       old = locinput;
+                       st->plus.old = locinput;
                        if (do_utf8)
                            locinput += UTF8SKIP(locinput);
                        else
                            locinput++;
-                       count = 1;
+                       st->plus.count = 1;
                    }
                }
                else
-               while (n >= ln || (n == REG_INFTY && ln > 0)) { /* ln overflow ? */
+               while (n >= st->ln || (n == REG_INFTY && st->ln > 0)) { /* ln overflow ? */
                    UV c;
-                   if (c1 != -1000) {
+                   if (st->plus.c1 != -1000) {
                        if (do_utf8)
                            c = utf8n_to_uvchr((U8*)PL_reginput,
-                                              UTF8_MAXLEN, 0,
-                                              ckWARN(WARN_UTF8) ?
-                                              0 : UTF8_ALLOW_ANY);
+                                              UTF8_MAXBYTES, 0,
+                                              uniflags);
                        else
                            c = UCHARAT(PL_reginput);
                        /* If it could work, try it. */
-                       if (c == (UV)c1 || c == (UV)c2)
+                       if (c == (UV)st->plus.c1 || c == (UV)st->plus.c2)
                        {
-                           TRYPAREN(paren, ln, PL_reginput);
-                           REGCP_UNWIND(lastcp);
+                           TRYPAREN(st->plus.paren, st->ln, PL_reginput, PLUS2);
+                           /*** all unsaved local vars undefined at this point */
+                           REGCP_UNWIND(st->plus.lastcp);
                        }
                    }
                    /* If it could work, try it. */
-                   else if (c1 == -1000)
+                   else if (st->plus.c1 == -1000)
                    {
-                       TRYPAREN(paren, ln, PL_reginput);
-                       REGCP_UNWIND(lastcp);
+                       TRYPAREN(st->plus.paren, st->ln, PL_reginput, PLUS3);
+                       /*** all unsaved local vars undefined at this point */
+                       REGCP_UNWIND(st->plus.lastcp);
                    }
                    /* Couldn't or didn't -- move forward. */
                    PL_reginput = locinput;
                    if (regrepeat(scan, 1)) {
-                       ln++;
+                       st->ln++;
                        locinput = PL_reginput;
                    }
                    else
@@ -3703,61 +4200,37 @@ S_regmatch(pTHX_ regnode *prog)
                }
            }
            else {
-               CHECKPOINT lastcp;
                n = regrepeat(scan, n);
                locinput = PL_reginput;
-               if (ln < n && PL_regkind[(U8)OP(next)] == EOL &&
-                   ((!PL_multiline && OP(next) != MEOL) ||
+               if (st->ln < n && PL_regkind[(U8)OP(next)] == EOL &&
+                   (OP(next) != MEOL ||
                        OP(next) == SEOL || OP(next) == EOS))
                {
-                   ln = n;                     /* why back off? */
+                   st->ln = n;                 /* why back off? */
                    /* ...because $ and \Z can match before *and* after
                       newline at the end.  Consider "\n\n" =~ /\n+\Z\n/.
                       We should back off by one in this case. */
                    if (UCHARAT(PL_reginput - 1) == '\n' && OP(next) != EOS)
-                       ln--;
-               }
-               REGCP_SET(lastcp);
-               if (paren) {
-                   UV c = 0;
-                   while (n >= ln) {
-                       if (c1 != -1000) {
-                           if (do_utf8)
-                               c = utf8n_to_uvchr((U8*)PL_reginput,
-                                                  UTF8_MAXLEN, 0,
-                                                  ckWARN(WARN_UTF8) ?
-                                                  0 : UTF8_ALLOW_ANY);
-                           else
-                               c = UCHARAT(PL_reginput);
-                       }
-                       /* If it could work, try it. */
-                       if (c1 == -1000 || c == (UV)c1 || c == (UV)c2)
-                           {
-                               TRYPAREN(paren, n, PL_reginput);
-                               REGCP_UNWIND(lastcp);
-                           }
-                       /* Couldn't or didn't -- back up. */
-                       n--;
-                       PL_reginput = locinput = HOPc(locinput, -1);
-                   }
+                       st->ln--;
                }
-               else {
+               REGCP_SET(st->plus.lastcp);
+               {
                    UV c = 0;
-                   while (n >= ln) {
-                       if (c1 != -1000) {
+                   while (n >= st->ln) {
+                       if (st->plus.c1 != -1000) {
                            if (do_utf8)
                                c = utf8n_to_uvchr((U8*)PL_reginput,
-                                                  UTF8_MAXLEN, 0,
-                                                  ckWARN(WARN_UTF8) ?
-                                                  0 : UTF8_ALLOW_ANY);
+                                                  UTF8_MAXBYTES, 0,
+                                                  uniflags);
                            else
                                c = UCHARAT(PL_reginput);
                        }
                        /* If it could work, try it. */
-                       if (c1 == -1000 || c == (UV)c1 || c == (UV)c2)
+                       if (st->plus.c1 == -1000 || c == (UV)st->plus.c1 || c == (UV)st->plus.c2)
                            {
-                               TRYPAREN(paren, n, PL_reginput);
-                               REGCP_UNWIND(lastcp);
+                               TRYPAREN(st->plus.paren, n, PL_reginput, PLUS4);
+                               /*** all unsaved local vars undefined at this point */
+                               REGCP_UNWIND(st->plus.lastcp);
                            }
                        /* Couldn't or didn't -- back up. */
                        n--;
@@ -3769,33 +4242,43 @@ S_regmatch(pTHX_ regnode *prog)
            break;
        case END:
            if (PL_reg_call_cc) {
-               re_cc_state *cur_call_cc = PL_reg_call_cc;
-               CURCUR *cctmp = PL_regcc;
-               regexp *re = PL_reg_re;
-               CHECKPOINT cp, lastcp;
-               
-               cp = regcppush(0);      /* Save *all* the positions. */
-               REGCP_SET(lastcp);
-               regcp_set_to(PL_reg_call_cc->ss); /* Restore parens of
-                                                   the caller. */
-               PL_reginput = locinput; /* Make position available to
-                                          the callcc. */
+               st->end.cur_call_cc = PL_reg_call_cc;
+               st->end.end_re = PL_reg_re;
+
+               /* Save *all* the positions. */
+               st->end.cp = regcppush(0);
+               REGCP_SET(st->end.lastcp);
+
+               /* Restore parens of the caller. */
+               {
+                   I32 tmp = PL_savestack_ix;
+                   PL_savestack_ix = PL_reg_call_cc->ss;
+                   regcppop();
+                   PL_savestack_ix = tmp;
+               }
+
+               /* Make position available to the callcc. */
+               PL_reginput = locinput;
+
                cache_re(PL_reg_call_cc->re);
-               PL_regcc = PL_reg_call_cc->cc;
+               st->end.savecc = st->cc;
+               st->cc = PL_reg_call_cc->cc;
                PL_reg_call_cc = PL_reg_call_cc->prev;
-               if (regmatch(cur_call_cc->node)) {
-                   PL_reg_call_cc = cur_call_cc;
-                   regcpblow(cp);
+               REGMATCH(st->end.cur_call_cc->node, END);
+               /*** all unsaved local vars undefined at this point */
+               if (result) {
+                   PL_reg_call_cc = st->end.cur_call_cc;
+                   regcpblow(st->end.cp);
                    sayYES;
                }
-               REGCP_UNWIND(lastcp);
+               REGCP_UNWIND(st->end.lastcp);
                regcppop();
-               PL_reg_call_cc = cur_call_cc;
-               PL_regcc = cctmp;
-               PL_reg_re = re;
-               cache_re(re);
+               PL_reg_call_cc = st->end.cur_call_cc;
+               st->cc = st->end.savecc;
+               PL_reg_re = st->end.end_re;
+               cache_re(st->end.end_re);
 
-               DEBUG_r(
+               DEBUG_EXECUTE_r(
                    PerlIO_printf(Perl_debug_log,
                                  "%*s  continuation failed...\n",
                                  REPORT_CODE_OFF+PL_regindent*2, "")
@@ -3803,7 +4286,7 @@ S_regmatch(pTHX_ regnode *prog)
                sayNO_SILENT;
            }
            if (locinput < PL_regtill) {
-               DEBUG_r(PerlIO_printf(Perl_debug_log,
+               DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log,
                                      "%sMatch possible, but length=%ld is smaller than requested=%ld, failing!%s\n",
                                      PL_colors[4],
                                      (long)(locinput - PL_reg_starttry),
@@ -3823,7 +4306,7 @@ S_regmatch(pTHX_ regnode *prog)
        case UNLESSM:
            n = 0;
            if (scan->flags) {
-               s = HOPBACKc(locinput, scan->flags);
+               char * const s = HOPBACKc(locinput, scan->flags);
                if (!s)
                    goto say_yes;
                PL_reginput = s;
@@ -3834,7 +4317,7 @@ S_regmatch(pTHX_ regnode *prog)
        case IFMATCH:
            n = 1;
            if (scan->flags) {
-               s = HOPBACKc(locinput, scan->flags);
+               char * const s = HOPBACKc(locinput, scan->flags);
                if (!s)
                    goto say_no;
                PL_reginput = s;
@@ -3843,21 +4326,22 @@ S_regmatch(pTHX_ regnode *prog)
                PL_reginput = locinput;
 
          do_ifmatch:
-           inner = NEXTOPER(NEXTOPER(scan));
-           if (regmatch(inner) != n) {
+           REGMATCH(NEXTOPER(NEXTOPER(scan)), IFMATCH);
+           /*** all unsaved local vars undefined at this point */
+           if (result != n) {
              say_no:
-               if (logical) {
-                   logical = 0;
-                   sw = 0;
+               if (st->logical) {
+                   st->logical = 0;
+                   st->sw = 0;
                    goto do_longjump;
                }
                else
                    sayNO;
            }
          say_yes:
-           if (logical) {
-               logical = 0;
-               sw = 1;
+           if (st->logical) {
+               st->logical = 0;
+               st->sw = 1;
            }
            if (OP(scan) == SUSPEND) {
                locinput = PL_reginput;
@@ -3875,8 +4359,46 @@ S_regmatch(pTHX_ regnode *prog)
                          PTR2UV(scan), OP(scan));
            Perl_croak(aTHX_ "regexp memory corruption");
        }
+
       reenter:
        scan = next;
+       continue;
+       /* NOTREACHED */
+
+       /* simulate recursively calling regmatch(), but without actually
+        * recursing - ie save the current state on the heap rather than on
+        * the stack, then re-enter the loop. This avoids complex regexes
+        * blowing the processor stack */
+
+      start_recurse:
+       {
+           /* push new state */
+           regmatch_state *oldst = st;
+
+           depth++;
+
+           /* grab the next free state slot */
+           st++;
+           if (st >  &(PL_regmatch_slab->states[PERL_REGMATCH_SLAB_SLOTS-1]))
+               st = S_push_slab(aTHX);
+           PL_regmatch_state = st;
+
+           oldst->next = next;
+           oldst->n = n;
+           oldst->locinput = locinput;
+           oldst->reg_call_cc = PL_reg_call_cc;
+
+           st->cc = oldst->cc;
+           locinput = PL_reginput;
+           nextchr = UCHARAT(locinput);
+           st->minmod = 0;
+           st->sw = 0;
+           st->logical = 0;
+           st->unwind = 0;
+#ifdef DEBUGGING
+           PL_regindent++;
+#endif
+       }
     }
 
     /*
@@ -3888,44 +4410,41 @@ S_regmatch(pTHX_ regnode *prog)
     sayNO;
 
 yes_loud:
-    DEBUG_r(
+    DEBUG_EXECUTE_r(
        PerlIO_printf(Perl_debug_log,
                      "%*s  %scould match...%s\n",
-                     REPORT_CODE_OFF+PL_regindent*2, "", PL_colors[4],PL_colors[5])
+                     REPORT_CODE_OFF+PL_regindent*2, "", PL_colors[4], PL_colors[5])
        );
     goto yes;
 yes_final:
-    DEBUG_r(PerlIO_printf(Perl_debug_log, "%sMatch successful!%s\n",
-                         PL_colors[4],PL_colors[5]));
+    DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "%sMatch successful!%s\n",
+                         PL_colors[4], PL_colors[5]));
 yes:
 #ifdef DEBUGGING
     PL_regindent--;
 #endif
 
-#if 0                                  /* Breaks $^R */
-    if (unwind)
-       regcpblow(firstcp);
-#endif
-    return 1;
+    result = 1;
+    goto exit_level;
 
 no:
-    DEBUG_r(
+    DEBUG_EXECUTE_r(
        PerlIO_printf(Perl_debug_log,
                      "%*s  %sfailed...%s\n",
-                     REPORT_CODE_OFF+PL_regindent*2, "",PL_colors[4],PL_colors[5])
+                     REPORT_CODE_OFF+PL_regindent*2, "", PL_colors[4], PL_colors[5])
        );
     goto do_no;
 no_final:
 do_no:
-    if (unwind) {
-       re_unwind_t *uw = SSPTRt(unwind,re_unwind_t);
+    if (st->unwind) {
+       re_unwind_t * const uw = SSPTRt(st->unwind,re_unwind_t);
 
        switch (uw->type) {
        case RE_UNWIND_BRANCH:
        case RE_UNWIND_BRANCHJ:
        {
-           re_unwind_branch_t *uwb = &(uw->branch);
-           I32 lastparen = uwb->lastparen;
+           re_unwind_branch_t * const uwb = &(uw->branch);
+           const I32 lastparen = uwb->lastparen;
        
            REGCP_UNWIND(uwb->lastcp);
            for (n = *PL_reglastparen; n > lastparen; n--)
@@ -3935,14 +4454,13 @@ do_no:
            if ( !scan ||
                 OP(scan) != (uwb->type == RE_UNWIND_BRANCH
                              ? BRANCH : BRANCHJ) ) {           /* Failure */
-               unwind = uwb->prev;
+               st->unwind = uwb->prev;
 #ifdef DEBUGGING
                PL_regindent--;
 #endif
                goto do_no;
            }
            /* Have more choice yet.  Reuse the same uwb.  */
-           /*SUPPRESS 560*/
            if ((n = (uwb->type == RE_UNWIND_BRANCH
                      ? NEXT_OFF(next) : ARG(next))))
                next += n;
@@ -3960,16 +4478,94 @@ do_no:
 
            goto reenter;
        }
-       /* NOT REACHED */
+       /* NOTREACHED */
        default:
            Perl_croak(aTHX_ "regexp unwind memory corruption");
        }
-       /* NOT REACHED */
+       /* NOTREACHED */
     }
 #ifdef DEBUGGING
     PL_regindent--;
 #endif
-    return 0;
+    result = 0;
+exit_level:
+
+    if (depth--) {
+       /* restore previous state and re-enter */
+       st--;
+       if (st < &PL_regmatch_slab->states[0]) {
+           PL_regmatch_slab = PL_regmatch_slab->prev;
+           st = &PL_regmatch_slab->states[PERL_REGMATCH_SLAB_SLOTS-1];
+       }
+       PL_regmatch_state = st;
+
+       PL_reg_call_cc  = st->reg_call_cc;
+       scan            = st->scan;
+       next            = st->next;
+       n               = st->n;
+       locinput        = st->locinput;
+       nextchr = UCHARAT(locinput);
+
+       switch (st->resume_state) {
+       case resume_TRIE1:
+           goto resume_point_TRIE1;
+       case resume_TRIE2:
+           goto resume_point_TRIE2;
+       case resume_CURLYX:
+           goto resume_point_CURLYX;
+       case resume_WHILEM1:
+           goto resume_point_WHILEM1;
+       case resume_WHILEM2:
+           goto resume_point_WHILEM2;
+       case resume_WHILEM3:
+           goto resume_point_WHILEM3;
+       case resume_WHILEM4:
+           goto resume_point_WHILEM4;
+       case resume_WHILEM5:
+           goto resume_point_WHILEM5;
+       case resume_WHILEM6:
+           goto resume_point_WHILEM6;
+       case resume_CURLYM1:
+           goto resume_point_CURLYM1;
+       case resume_CURLYM2:
+           goto resume_point_CURLYM2;
+       case resume_CURLYM3:
+           goto resume_point_CURLYM3;
+       case resume_CURLYM4:
+           goto resume_point_CURLYM4;
+       case resume_IFMATCH:
+           goto resume_point_IFMATCH;
+       case resume_PLUS1:
+           goto resume_point_PLUS1;
+       case resume_PLUS2:
+           goto resume_point_PLUS2;
+       case resume_PLUS3:
+           goto resume_point_PLUS3;
+       case resume_PLUS4:
+           goto resume_point_PLUS4;
+       case resume_END:
+           goto resume_point_END;
+       default:
+           Perl_croak(aTHX_ "regexp resume memory corruption");
+       }
+       /* NOTREACHED */
+    }
+    /* restore original high-water mark */
+    PL_regmatch_slab  = orig_slab;
+    PL_regmatch_state = orig_state;
+
+    /* free all slabs above current one */
+    if (orig_slab->next) {
+       regmatch_slab *osl, *sl = orig_slab->next;
+       orig_slab->next = NULL;
+       while (sl) {
+           osl = sl;
+           sl = sl->next;
+       }
+    }
+
+    return result;
+
 }
 
 /*
@@ -3981,8 +4577,9 @@ do_no:
  * rather than incrementing count on every character.  [Er, except utf8.]]
  */
 STATIC I32
-S_regrepeat(pTHX_ regnode *p, I32 max)
+S_regrepeat(pTHX_ const regnode *p, I32 max)
 {
+    dVAR;
     register char *scan;
     register I32 c;
     register char *loceol = PL_regeol;
@@ -4055,7 +4652,7 @@ S_regrepeat(pTHX_ regnode *p, I32 max)
     case ALNUM:
        if (do_utf8) {
            loceol = PL_regeol;
-           LOAD_UTF8_CHARCLASS(alnum,"a");
+           LOAD_UTF8_CHARCLASS_ALNUM();
            while (hardcount < max && scan < loceol &&
                   swash_fetch(PL_utf8_alnum, (U8*)scan, do_utf8)) {
                scan += UTF8SKIP(scan);
@@ -4083,7 +4680,7 @@ S_regrepeat(pTHX_ regnode *p, I32 max)
     case NALNUM:
        if (do_utf8) {
            loceol = PL_regeol;
-           LOAD_UTF8_CHARCLASS(alnum,"a");
+           LOAD_UTF8_CHARCLASS_ALNUM();
            while (hardcount < max && scan < loceol &&
                   !swash_fetch(PL_utf8_alnum, (U8*)scan, do_utf8)) {
                scan += UTF8SKIP(scan);
@@ -4111,7 +4708,7 @@ S_regrepeat(pTHX_ regnode *p, I32 max)
     case SPACE:
        if (do_utf8) {
            loceol = PL_regeol;
-           LOAD_UTF8_CHARCLASS(space," ");
+           LOAD_UTF8_CHARCLASS_SPACE();
            while (hardcount < max && scan < loceol &&
                   (*scan == ' ' ||
                    swash_fetch(PL_utf8_space,(U8*)scan, do_utf8))) {
@@ -4140,7 +4737,7 @@ S_regrepeat(pTHX_ regnode *p, I32 max)
     case NSPACE:
        if (do_utf8) {
            loceol = PL_regeol;
-           LOAD_UTF8_CHARCLASS(space," ");
+           LOAD_UTF8_CHARCLASS_SPACE();
            while (hardcount < max && scan < loceol &&
                   !(*scan == ' ' ||
                     swash_fetch(PL_utf8_space,(U8*)scan, do_utf8))) {
@@ -4169,7 +4766,7 @@ S_regrepeat(pTHX_ regnode *p, I32 max)
     case DIGIT:
        if (do_utf8) {
            loceol = PL_regeol;
-           LOAD_UTF8_CHARCLASS(digit,"0");
+           LOAD_UTF8_CHARCLASS_DIGIT();
            while (hardcount < max && scan < loceol &&
                   swash_fetch(PL_utf8_digit, (U8*)scan, do_utf8)) {
                scan += UTF8SKIP(scan);
@@ -4183,7 +4780,7 @@ S_regrepeat(pTHX_ regnode *p, I32 max)
     case NDIGIT:
        if (do_utf8) {
            loceol = PL_regeol;
-           LOAD_UTF8_CHARCLASS(digit,"0");
+           LOAD_UTF8_CHARCLASS_DIGIT();
            while (hardcount < max && scan < loceol &&
                   !swash_fetch(PL_utf8_digit, (U8*)scan, do_utf8)) {
                scan += UTF8SKIP(scan);
@@ -4204,96 +4801,48 @@ S_regrepeat(pTHX_ regnode *p, I32 max)
        c = scan - PL_reginput;
     PL_reginput = scan;
 
-    DEBUG_r(
-       {
-               SV *prop = sv_newmortal();
-
+    DEBUG_r({
+               SV *re_debug_flags = NULL;
+               SV * const prop = sv_newmortal();
+                GET_RE_DEBUG_FLAGS;
+                DEBUG_EXECUTE_r({
                regprop(prop, p);
                PerlIO_printf(Perl_debug_log,
                              "%*s  %s can match %"IVdf" times out of %"IVdf"...\n",
-                             REPORT_CODE_OFF+1, "", SvPVX(prop),(IV)c,(IV)max);
+                             REPORT_CODE_OFF+1, "", SvPVX_const(prop),(IV)c,(IV)max);
+       });
        });
 
     return(c);
 }
 
-/*
- - regrepeat_hard - repeatedly match something, report total lenth and length
- *
- * The repeater is supposed to have constant length.
- */
-
-STATIC I32
-S_regrepeat_hard(pTHX_ regnode *p, I32 max, I32 *lp)
-{
-    register char *scan = Nullch;
-    register char *start;
-    register char *loceol = PL_regeol;
-    I32 l = 0;
-    I32 count = 0, res = 1;
-
-    if (!max)
-       return 0;
-
-    start = PL_reginput;
-    if (PL_reg_match_utf8) {
-       while (PL_reginput < loceol && (scan = PL_reginput, res = regmatch(p))) {
-           if (!count++) {
-               l = 0;
-               while (start < PL_reginput) {
-                   l++;
-                   start += UTF8SKIP(start);
-               }
-               *lp = l;
-               if (l == 0)
-                   return max;
-           }
-           if (count == max)
-               return count;
-       }
-    }
-    else {
-       while (PL_reginput < loceol && (scan = PL_reginput, res = regmatch(p))) {
-           if (!count++) {
-               *lp = l = PL_reginput - start;
-               if (max != REG_INFTY && l*max < loceol - scan)
-                   loceol = scan + l*max;
-               if (l == 0)
-                   return max;
-           }
-       }
-    }
-    if (!res)
-       PL_reginput = scan;
-
-    return count;
-}
 
 /*
 - regclass_swash - prepare the utf8 swash
 */
 
 SV *
-Perl_regclass_swash(pTHX_ register regnode* node, bool doinit, SV** listsvp, SV **altsvp)
+Perl_regclass_swash(pTHX_ register const regnode* node, bool doinit, SV** listsvp, SV **altsvp)
 {
+    dVAR;
     SV *sw  = NULL;
     SV *si  = NULL;
     SV *alt = NULL;
 
     if (PL_regdata && PL_regdata->count) {
-       U32 n = ARG(node);
+       const U32 n = ARG(node);
 
        if (PL_regdata->what[n] == 's') {
-           SV *rv = (SV*)PL_regdata->data[n];
-           AV *av = (AV*)SvRV((SV*)rv);
-           SV **ary = AvARRAY(av);
+           SV * const rv = (SV*)PL_regdata->data[n];
+           AV * const av = (AV*)SvRV((SV*)rv);
+           SV **const ary = AvARRAY(av);
            SV **a, **b;
        
-           /* See the end of regcomp.c:S_reglass() for
+           /* See the end of regcomp.c:S_regclass() for
             * documentation of these array elements. */
 
            si = *ary;
-           a  = SvTYPE(ary[1]) == SVt_RV   ? &ary[1] : 0;
+           a  = SvROK(ary[1]) ? &ary[1] : 0;
            b  = SvTYPE(ary[2]) == SVt_PVAV ? &ary[2] : 0;
 
            if (a)
@@ -4326,17 +4875,22 @@ Perl_regclass_swash(pTHX_ register regnode* node, bool doinit, SV** listsvp, SV
  */
 
 STATIC bool
-S_reginclass(pTHX_ register regnode *n, register U8* p, STRLEN* lenp, register bool do_utf8)
+S_reginclass(pTHX_ register const regnode *n, register const U8* p, STRLEN* lenp, register bool do_utf8)
 {
-    char flags = ANYOF_FLAGS(n);
+    dVAR;
+    const char flags = ANYOF_FLAGS(n);
     bool match = FALSE;
     UV c = *p;
     STRLEN len = 0;
     STRLEN plen;
 
-    if (do_utf8 && !UTF8_IS_INVARIANT(c))
-        c = utf8n_to_uvchr(p, UTF8_MAXLEN, &len,
-                           ckWARN(WARN_UTF8) ? 0 : UTF8_ALLOW_ANY);
+    if (do_utf8 && !UTF8_IS_INVARIANT(c)) {
+       c = utf8n_to_uvchr(p, UTF8_MAXBYTES, &len,
+                           ckWARN(WARN_UTF8) ? UTF8_CHECK_ONLY :
+                                       UTF8_ALLOW_ANYUV|UTF8_CHECK_ONLY);
+       if (len == (STRLEN)-1)
+           Perl_croak(aTHX_ "Malformed UTF-8 character (fatal)");
+    }
 
     plen = lenp ? *lenp : UNISKIP(NATIVE_TO_UNI(c));
     if (do_utf8 || (flags & ANYOF_UNICODE)) {
@@ -4350,7 +4904,7 @@ S_reginclass(pTHX_ register regnode *n, register U8* p, STRLEN* lenp, register b
            match = TRUE;
        if (!match) {
            AV *av;
-           SV *sw = regclass_swash(n, TRUE, 0, (SV**)&av);
+           SV * const sw = regclass_swash(n, TRUE, 0, (SV**)&av);
        
            if (sw) {
                if (swash_fetch(sw, p, do_utf8))
@@ -4358,11 +4912,10 @@ S_reginclass(pTHX_ register regnode *n, register U8* p, STRLEN* lenp, register b
                else if (flags & ANYOF_FOLD) {
                    if (!match && lenp && av) {
                        I32 i;
-                     
                        for (i = 0; i <= av_len(av); i++) {
-                           SV* sv = *av_fetch(av, i, FALSE);
+                           SV* const sv = *av_fetch(av, i, FALSE);
                            STRLEN len;
-                           char *s = SvPV(sv, len);
+                           const char * const s = SvPV_const(sv, len);
                        
                            if (len <= plen && memEQ(s, (char*)p, len)) {
                                *lenp = len;
@@ -4372,7 +4925,7 @@ S_reginclass(pTHX_ register regnode *n, register U8* p, STRLEN* lenp, register b
                        }
                    }
                    if (!match) {
-                       U8 tmpbuf[UTF8_MAXLEN_FOLD+1];
+                       U8 tmpbuf[UTF8_MAXBYTES_CASE+1];
                        STRLEN tmplen;
 
                        to_utf8_fold(p, tmpbuf, &tmplen);
@@ -4445,14 +4998,9 @@ S_reginclass(pTHX_ register regnode *n, register U8* p, STRLEN* lenp, register b
 }
 
 STATIC U8 *
-S_reghop(pTHX_ U8 *s, I32 off)
-{
-    return S_reghop3(aTHX_ s, off, (U8*)(off >= 0 ? PL_regeol : PL_bostr));
-}
-
-STATIC U8 *
-S_reghop3(pTHX_ U8 *s, I32 off, U8* lim)
+S_reghop3(U8 *s, I32 off, U8* lim)
 {
+    dVAR;
     if (off >= 0) {
        while (off-- && s < lim) {
            /* XXX could check well-formedness here */
@@ -4475,14 +5023,9 @@ S_reghop3(pTHX_ U8 *s, I32 off, U8* lim)
 }
 
 STATIC U8 *
-S_reghopmaybe(pTHX_ U8 *s, I32 off)
-{
-    return S_reghopmaybe3(aTHX_ s, off, (U8*)(off >= 0 ? PL_regeol : PL_bostr));
-}
-
-STATIC U8 *
-S_reghopmaybe3(pTHX_ U8* s, I32 off, U8* lim)
+S_reghopmaybe3(U8* s, I32 off, U8* lim)
 {
+    dVAR;
     if (off >= 0) {
        while (off-- && s < lim) {
            /* XXX could check well-formedness here */
@@ -4513,10 +5056,15 @@ S_reghopmaybe3(pTHX_ U8* s, I32 off, U8* lim)
 static void
 restore_pos(pTHX_ void *arg)
 {
+    dVAR;
+    PERL_UNUSED_ARG(arg);
     if (PL_reg_eval_set) {
        if (PL_reg_oldsaved) {
            PL_reg_re->subbeg = PL_reg_oldsaved;
            PL_reg_re->sublen = PL_reg_oldsavedlen;
+#ifdef PERL_OLD_COPY_ON_WRITE
+           PL_reg_re->saved_copy = PL_nrs;
+#endif
            RX_MATCH_COPIED_on(PL_reg_re);
        }
        PL_reg_magic->mg_len = PL_reg_oldpos;
@@ -4528,10 +5076,9 @@ restore_pos(pTHX_ void *arg)
 STATIC void
 S_to_utf8_substr(pTHX_ register regexp *prog)
 {
-    SV* sv;
     if (prog->float_substr && !prog->float_utf8) {
-       prog->float_utf8 = sv = NEWSV(117, 0);
-       SvSetSV(sv, prog->float_substr);
+       SV* sv;
+       prog->float_utf8 = sv = newSVsv(prog->float_substr);
        sv_utf8_upgrade(sv);
        if (SvTAIL(prog->float_substr))
            SvTAIL_on(sv);
@@ -4539,8 +5086,8 @@ S_to_utf8_substr(pTHX_ register regexp *prog)
            prog->check_utf8 = sv;
     }
     if (prog->anchored_substr && !prog->anchored_utf8) {
-       prog->anchored_utf8 = sv = NEWSV(118, 0);
-       SvSetSV(sv, prog->anchored_substr);
+       SV* sv;
+       prog->anchored_utf8 = sv = newSVsv(prog->anchored_substr);
        sv_utf8_upgrade(sv);
        if (SvTAIL(prog->anchored_substr))
            SvTAIL_on(sv);
@@ -4552,10 +5099,10 @@ S_to_utf8_substr(pTHX_ register regexp *prog)
 STATIC void
 S_to_byte_substr(pTHX_ register regexp *prog)
 {
-    SV* sv;
+    dVAR;
     if (prog->float_utf8 && !prog->float_substr) {
-       prog->float_substr = sv = NEWSV(117, 0);
-       SvSetSV(sv, prog->float_utf8);
+       SV* sv;
+       prog->float_substr = sv = newSVsv(prog->float_utf8);
        if (sv_utf8_downgrade(sv, TRUE)) {
            if (SvTAIL(prog->float_utf8))
                SvTAIL_on(sv);
@@ -4567,8 +5114,8 @@ S_to_byte_substr(pTHX_ register regexp *prog)
            prog->check_substr = sv;
     }
     if (prog->anchored_utf8 && !prog->anchored_substr) {
-       prog->anchored_substr = sv = NEWSV(118, 0);
-       SvSetSV(sv, prog->anchored_utf8);
+       SV* sv;
+       prog->anchored_substr = sv = newSVsv(prog->anchored_utf8);
        if (sv_utf8_downgrade(sv, TRUE)) {
            if (SvTAIL(prog->anchored_utf8))
                SvTAIL_on(sv);
@@ -4580,3 +5127,13 @@ S_to_byte_substr(pTHX_ register regexp *prog)
            prog->check_substr = sv;
     }
 }
+
+/*
+ * Local variables:
+ * c-indentation-style: bsd
+ * c-basic-offset: 4
+ * indent-tabs-mode: t
+ * End:
+ *
+ * ex: set ts=8 sts=4 sw=4 noet:
+ */