This is a live mirror of the Perl 5 development currently hosted at https://github.com/perl/perl5
generalize the 'continue on success' mechanism of deferred REs
[perl5.git] / regexec.c
index 13cc68b..4d0388d 100644 (file)
--- a/regexec.c
+++ b/regexec.c
@@ -78,7 +78,7 @@
  ****    Alterations to Henry's code are...
  ****
  ****    Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
- ****    2000, 2001, 2002, 2003, 2004, 2005, by Larry Wall and others
+ ****    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        STATIC  static
 #endif
 
-#define REGINCLASS(p,c)  (ANYOF_FLAGS(p) ? reginclass(p,c,0,0) : ANYOF_BITMAP_TEST(p,*(c)))
+#define REGINCLASS(prog,p,c)  (ANYOF_FLAGS(p) ? reginclass(prog,p,c,0,0) : ANYOF_BITMAP_TEST(p,*(c)))
 
 /*
  * Forwards.
 #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(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
@@ -178,6 +170,7 @@ static void restore_pos(pTHX_ void *arg);
 STATIC CHECKPOINT
 S_regcppush(pTHX_ I32 parenfloor)
 {
+    dVAR;
     const int retval = PL_savestack_ix;
 #define REGCP_PAREN_ELEMS 4
     const int paren_elems_to_push = (PL_regsize - parenfloor) * REGCP_PAREN_ELEMS;
@@ -220,10 +213,10 @@ S_regcppush(pTHX_ I32 parenfloor)
                                (IV)(cp), (IV)PL_savestack_ix) : 0); regcpblow(cp)
 
 STATIC char *
-S_regcppop(pTHX)
+S_regcppop(pTHX_ const regexp *rex)
 {
+    dVAR;
     I32 i;
-    U32 paren = 0;
     char *input;
 
     GET_RE_DEBUG_FLAGS_DECL;
@@ -241,7 +234,7 @@ S_regcppop(pTHX)
     for (i -= (REGCP_OTHER_ELEMS - REGCP_FRAME_ELEMS);
         i > 0; i -= REGCP_PAREN_ELEMS) {
        I32 tmps;
-       paren = (U32)SSPOPINT;
+       U32 paren = (U32)SSPOPINT;
        PL_reg_start_tmp[paren] = (char *) SSPOPPTR;
        PL_regstartp[paren] = SSPOPINT;
        tmps = SSPOPINT;
@@ -257,10 +250,10 @@ S_regcppop(pTHX)
        );
     }
     DEBUG_EXECUTE_r(
-       if ((I32)(*PL_reglastparen + 1) <= PL_regnpar) {
+       if ((I32)(*PL_reglastparen + 1) <= rex->nparens) {
            PerlIO_printf(Perl_debug_log,
                          "     restoring \\%"IVdf"..\\%"IVdf" to undef\n",
-                         (IV)(*PL_reglastparen + 1), (IV)PL_regnpar);
+                         (IV)(*PL_reglastparen + 1), (IV)rex->nparens);
        }
     );
 #if 1
@@ -274,38 +267,18 @@ S_regcppop(pTHX)
      * building DynaLoader will fail:
      * "Error: '*' not in typemap in DynaLoader.xs, line 164"
      * --jhi */
-    for (paren = *PL_reglastparen + 1; (I32)paren <= PL_regnpar; paren++) {
-       if ((I32)paren > PL_regsize)
-           PL_regstartp[paren] = -1;
-       PL_regendp[paren] = -1;
+    for (i = *PL_reglastparen + 1; i <= rex->nparens; i++) {
+       if (i > PL_regsize)
+           PL_regstartp[i] = -1;
+       PL_regendp[i] = -1;
     }
 #endif
     return input;
 }
 
-STATIC char *
-S_regcp_set_to(pTHX_ I32 ss)
-{
-    const 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;   \
@@ -314,7 +287,8 @@ 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;                                 \
@@ -341,17 +315,6 @@ Perl_pregexec(pTHX_ register regexp *prog, char *stringarg, register char *stren
                      nosave ? 0 : REXEC_COPY_STR);
 }
 
-STATIC void
-S_cache_re(pTHX_ regexp *prog)
-{
-    PL_regprecomp = prog->precomp;             /* Needed for FAIL. */
-#ifdef DEBUGGING
-    PL_regprogram = prog->program;
-#endif
-    PL_regnpar = prog->nparens;
-    PL_regdata = prog->data;
-    PL_reg_re = prog;
-}
 
 /*
  * Need to implement the following flags for reg_anch:
@@ -403,6 +366,7 @@ 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;
@@ -412,8 +376,8 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
     char *t;
     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
     const char * const i_strpos = strpos;
@@ -839,9 +803,9 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
            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
@@ -875,11 +839,10 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
                   : strend);
 
        t = s;
-       cache_re(prog);
-        s = find_byclass(prog, prog->regstclass, s, endpos, 1);
+        s = find_byclass(prog, prog->regstclass, s, endpos, NULL);
        if (!s) {
 #ifdef DEBUGGING
-           const char *what = 0;
+           const char *what = NULL;
 #endif
            if (endpos == strend) {
                DEBUG_EXECUTE_r( PerlIO_printf(Perl_debug_log,
@@ -964,12 +927,15 @@ Perl_re_intuit_start(pTHX_ regexp *prog, SV *sv, char *strpos,
   fail:
     DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "%sMatch rejected by optimizer%s\n",
                          PL_colors[4], PL_colors[5]));
-    return Nullch;
+    return NULL;
 }
 
 /* We know what class REx starts with.  Try to find this position... */
+/* if reginfo is NULL, its a dryrun */
+
 STATIC char *
-S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32 norun)
+S_find_byclass(pTHX_ regexp * prog, const regnode *c, char *s, const char
+*strend, const regmatch_info *reginfo)
 {
        dVAR;
        const I32 doevery = (prog->reganch & ROPT_SKIP) == 0;
@@ -990,9 +956,9 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                 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)))
+                         reginclass(prog, c, (U8*)s, 0, do_utf8) :
+                         REGINCLASS(prog, c, (U8*)s)) {
+                          if (tmp && (!reginfo || regtry(reginfo, s)))
                                goto got_it;
                           else
                                tmp = doevery;
@@ -1006,12 +972,12 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                 while (s < strend) {
                      STRLEN skip = 1;
 
-                     if (REGINCLASS(c, (U8*)s) ||
+                     if (REGINCLASS(prog, 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)))
+                          if (tmp && (!reginfo || regtry(reginfo, s)))
                                goto got_it;
                           else
                                tmp = doevery;
@@ -1024,7 +990,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
            break;
        case CANY:
            while (s < strend) {
-               if (tmp && (norun || regtry(prog, s)))
+               if (tmp && (!reginfo || regtry(reginfo, s)))
                    goto got_it;
                else
                    tmp = doevery;
@@ -1040,7 +1006,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                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;
+               const U32 uniflags = UTF8_ALLOW_DEFAULT;
 
                to_utf8_lower((U8*)m, tmpbuf1, &ulen1);
                to_utf8_upper((U8*)m, tmpbuf2, &ulen2);
@@ -1069,7 +1035,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
          do_exactf:
            e = HOP3c(strend, -((I32)lnc), s);
 
-           if (norun && e < s)
+           if (!reginfo && e < s)
                e = s;                  /* Due to minlen logic of intuit() */
 
            /* The idea in the EXACTF* cases is to first find the
@@ -1087,7 +1053,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                UV c, f;
                U8 tmpbuf [UTF8_MAXBYTES+1];
                STRLEN len, foldlen;
-               const U32 uniflags = ckWARN(WARN_UTF8) ? 0 : UTF8_ALLOW_ANY;
+               const U32 uniflags = UTF8_ALLOW_DEFAULT;
                if (c1 == c2) {
                    /* Upper and lower of 1st char are equal -
                     * probably not a "letter". */
@@ -1098,7 +1064,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                             && (ln == len ||
                                 ibcmp_utf8(s, (char **)0, 0,  do_utf8,
                                            m, (char **)0, ln, (bool)UTF))
-                            && (norun || regtry(prog, s)) )
+                            && (!reginfo || regtry(reginfo, s)) )
                            goto got_it;
                        else {
                             U8 foldbuf[UTF8_MAXBYTES_CASE+1];
@@ -1111,7 +1077,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                                                  (char **)0, foldlen, do_utf8,
                                                  m,
                                                  (char **)0, ln, (bool)UTF))
-                                 && (norun || regtry(prog, s)) )
+                                 && (!reginfo || regtry(reginfo, s)) )
                                  goto got_it;
                        }
                        s += len;
@@ -1137,7 +1103,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                             && (ln == len ||
                                 ibcmp_utf8(s, (char **)0, 0,  do_utf8,
                                            m, (char **)0, ln, (bool)UTF))
-                            && (norun || regtry(prog, s)) )
+                            && (!reginfo || regtry(reginfo, s)) )
                            goto got_it;
                        else {
                             U8 foldbuf[UTF8_MAXBYTES_CASE+1];
@@ -1150,7 +1116,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                                                  (char **)0, foldlen, do_utf8,
                                                  m,
                                                  (char **)0, ln, (bool)UTF))
-                                 && (norun || regtry(prog, s)) )
+                                 && (!reginfo || regtry(reginfo, s)) )
                                  goto got_it;
                        }
                        s += len;
@@ -1164,7 +1130,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                             && (ln == 1 || !(OP(c) == EXACTF
                                              ? ibcmp(s, m, ln)
                                              : ibcmp_locale(s, m, ln)))
-                            && (norun || regtry(prog, s)) )
+                            && (!reginfo || regtry(reginfo, s)) )
                            goto got_it;
                        s++;
                    }
@@ -1174,7 +1140,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                             && (ln == 1 || !(OP(c) == EXACTF
                                              ? ibcmp(s, m, ln)
                                              : ibcmp_locale(s, m, ln)))
-                            && (norun || regtry(prog, s)) )
+                            && (!reginfo || regtry(reginfo, s)) )
                            goto got_it;
                        s++;
                    }
@@ -1188,9 +1154,8 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                if (s == PL_bostr)
                    tmp = '\n';
                else {
-                   U8 *r = reghop3((U8*)s, -1, (U8*)PL_bostr);
-               
-                   tmp = utf8n_to_uvchr(r, UTF8SKIP(r), 0, 0);
+                   U8 * const r = reghop3((U8*)s, -1, (U8*)PL_bostr);
+                   tmp = utf8n_to_uvchr(r, UTF8SKIP(r), 0, UTF8_ALLOW_DEFAULT);
                }
                tmp = ((OP(c) == BOUND ?
                        isALNUM_uni(tmp) : isALNUM_LC_uvchr(UNI_TO_NATIVE(tmp))) != 0);
@@ -1201,7 +1166,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                                 isALNUM_LC_utf8((U8*)s)))
                    {
                        tmp = !tmp;
-                       if ((norun || regtry(prog, s)))
+                       if ((!reginfo || regtry(reginfo, s)))
                            goto got_it;
                    }
                    s += uskip;
@@ -1214,13 +1179,13 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                    if (tmp ==
                        !(OP(c) == BOUND ? isALNUM(*s) : isALNUM_LC(*s))) {
                        tmp = !tmp;
-                       if ((norun || regtry(prog, s)))
+                       if ((!reginfo || regtry(reginfo, s)))
                            goto got_it;
                    }
                    s++;
                }
            }
-           if ((!prog->minlen && tmp) && (norun || regtry(prog, s)))
+           if ((!prog->minlen && tmp) && (!reginfo || regtry(reginfo, s)))
                goto got_it;
            break;
        case NBOUNDL:
@@ -1231,9 +1196,8 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                if (s == PL_bostr)
                    tmp = '\n';
                else {
-                   U8 *r = reghop3((U8*)s, -1, (U8*)PL_bostr);
-               
-                   tmp = utf8n_to_uvchr(r, UTF8SKIP(r), 0, 0);
+                   U8 * const r = reghop3((U8*)s, -1, (U8*)PL_bostr);
+                   tmp = utf8n_to_uvchr(r, UTF8SKIP(r), 0, UTF8_ALLOW_DEFAULT);
                }
                tmp = ((OP(c) == NBOUND ?
                        isALNUM_uni(tmp) : isALNUM_LC_uvchr(UNI_TO_NATIVE(tmp))) != 0);
@@ -1243,7 +1207,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                                 swash_fetch(PL_utf8_alnum, (U8*)s, do_utf8) :
                                 isALNUM_LC_utf8((U8*)s)))
                        tmp = !tmp;
-                   else if ((norun || regtry(prog, s)))
+                   else if ((!reginfo || regtry(reginfo, s)))
                        goto got_it;
                    s += uskip;
                }
@@ -1256,12 +1220,12 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                    if (tmp ==
                        !(OP(c) == NBOUND ? isALNUM(*s) : isALNUM_LC(*s)))
                        tmp = !tmp;
-                   else if ((norun || regtry(prog, s)))
+                   else if ((!reginfo || regtry(reginfo, s)))
                        goto got_it;
                    s++;
                }
            }
-           if ((!prog->minlen && !tmp) && (norun || regtry(prog, s)))
+           if ((!prog->minlen && !tmp) && (!reginfo || regtry(reginfo, s)))
                goto got_it;
            break;
        case ALNUM:
@@ -1269,7 +1233,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                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)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1282,7 +1246,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
            else {
                while (s < strend) {
                    if (isALNUM(*s)) {
-                       if (tmp && (norun || regtry(prog, s)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1298,7 +1262,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
            if (do_utf8) {
                while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (isALNUM_LC_utf8((U8*)s)) {
-                       if (tmp && (norun || regtry(prog, s)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1311,7 +1275,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
            else {
                while (s < strend) {
                    if (isALNUM_LC(*s)) {
-                       if (tmp && (norun || regtry(prog, s)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1327,7 +1291,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                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)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1340,7 +1304,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
            else {
                while (s < strend) {
                    if (!isALNUM(*s)) {
-                       if (tmp && (norun || regtry(prog, s)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1356,7 +1320,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
            if (do_utf8) {
                while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (!isALNUM_LC_utf8((U8*)s)) {
-                       if (tmp && (norun || regtry(prog, s)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1369,7 +1333,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
            else {
                while (s < strend) {
                    if (!isALNUM_LC(*s)) {
-                       if (tmp && (norun || regtry(prog, s)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1385,7 +1349,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                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)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1398,7 +1362,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
            else {
                while (s < strend) {
                    if (isSPACE(*s)) {
-                       if (tmp && (norun || regtry(prog, s)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1414,7 +1378,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
            if (do_utf8) {
                while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (*s == ' ' || isSPACE_LC_utf8((U8*)s)) {
-                       if (tmp && (norun || regtry(prog, s)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1427,7 +1391,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
            else {
                while (s < strend) {
                    if (isSPACE_LC(*s)) {
-                       if (tmp && (norun || regtry(prog, s)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1443,7 +1407,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                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)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1456,7 +1420,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
            else {
                while (s < strend) {
                    if (!isSPACE(*s)) {
-                       if (tmp && (norun || regtry(prog, s)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1472,7 +1436,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
            if (do_utf8) {
                while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (!(*s == ' ' || isSPACE_LC_utf8((U8*)s))) {
-                       if (tmp && (norun || regtry(prog, s)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1485,7 +1449,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
            else {
                while (s < strend) {
                    if (!isSPACE_LC(*s)) {
-                       if (tmp && (norun || regtry(prog, s)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1501,7 +1465,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                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)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1514,7 +1478,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
            else {
                while (s < strend) {
                    if (isDIGIT(*s)) {
-                       if (tmp && (norun || regtry(prog, s)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1530,7 +1494,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
            if (do_utf8) {
                while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (isDIGIT_LC_utf8((U8*)s)) {
-                       if (tmp && (norun || regtry(prog, s)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1543,7 +1507,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
            else {
                while (s < strend) {
                    if (isDIGIT_LC(*s)) {
-                       if (tmp && (norun || regtry(prog, s)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1559,7 +1523,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
                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)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1572,7 +1536,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
            else {
                while (s < strend) {
                    if (!isDIGIT(*s)) {
-                       if (tmp && (norun || regtry(prog, s)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1588,7 +1552,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
            if (do_utf8) {
                while (s + (uskip = UTF8SKIP(s)) <= strend) {
                    if (!isDIGIT_LC_utf8((U8*)s)) {
-                       if (tmp && (norun || regtry(prog, s)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1601,7 +1565,7 @@ S_find_byclass(pTHX_ regexp * prog, regnode *c, char *s, const char *strend, I32
            else {
                while (s < strend) {
                    if (!isDIGIT_LC(*s)) {
-                       if (tmp && (norun || regtry(prog, s)))
+                       if (tmp && (!reginfo || regtry(reginfo, s)))
                            goto got_it;
                        else
                            tmp = doevery;
@@ -1633,6 +1597,7 @@ 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;
@@ -1640,26 +1605,19 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
     I32 dontbother = 0;        /* how many characters not to try at end */
     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);
     const bool do_utf8 = DO_UTF8(sv);
-    const I32 multiline = prog->reganch & PMf_MULTILINE;
+    I32 multiline;
 #ifdef DEBUGGING
-    SV *dsv0 = PERL_DEBUG_PAD_ZERO(0);
-    SV *dsv1 = PERL_DEBUG_PAD_ZERO(1);
+    SV* dsv0;
+    SV* dsv1;
 #endif
+    regmatch_info reginfo;  /* create some info to pass to regtry etc */
 
     GET_RE_DEBUG_FLAGS_DECL;
 
     PERL_UNUSED_ARG(data);
-    RX_MATCH_UTF8_set(prog,do_utf8);
-
-    PL_regcc = 0;
-
-    cache_re(prog);
-#ifdef DEBUGGING
-    PL_regnarrate = DEBUG_r_TEST;
-#endif
 
     /* Be paranoid... */
     if (prog == NULL || startpos == NULL) {
@@ -1667,6 +1625,16 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
        return 0;
     }
 
+    multiline = prog->reganch & PMf_MULTILINE;
+    reginfo.prog = prog;
+
+#ifdef DEBUGGING
+    dsv0 = PERL_DEBUG_PAD_ZERO(0);
+    dsv1 = PERL_DEBUG_PAD_ZERO(1);
+#endif
+
+    RX_MATCH_UTF8_set(prog, do_utf8);
+
     minlen = prog->minlen;
     if (strend - startpos < minlen) {
         DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log,
@@ -1687,43 +1655,40 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
        PL_reg_flags |= RF_utf8;
 
     /* Mark beginning of line for ^ and lookbehind. */
-    PL_regbol = startpos;
+    reginfo.bol = startpos; /* XXX not used ??? */
     PL_bostr  = strbeg;
-    PL_reg_sv = sv;
+    reginfo.sv = sv;
 
     /* Mark end of line for $ (and such) */
     PL_regeol = strend;
 
     /* see how far we have to get to not match where we matched before */
-    PL_regtill = startpos+minend;
-
-    /* We start without call_cc context.  */
-    PL_reg_call_cc = 0;
+    reginfo.till = startpos+minend;
 
     /* If there is a "must appear" string, look for it. */
     s = startpos;
 
-    if (prog->reganch & ROPT_GPOS_SEEN) { /* Need to have PL_reg_ganch */
+    if (prog->reganch & ROPT_GPOS_SEEN) { /* Need to set reginfo->ganch */
        MAGIC *mg;
 
        if (flags & REXEC_IGNOREPOS)    /* Means: check only at start */
-           PL_reg_ganch = startpos;
+           reginfo.ganch = startpos;
        else if (sv && SvTYPE(sv) >= SVt_PVMG
                  && SvMAGIC(sv)
                  && (mg = mg_find(sv, PERL_MAGIC_regex_global))
                  && mg->mg_len >= 0) {
-           PL_reg_ganch = strbeg + mg->mg_len; /* Defined pos() */
+           reginfo.ganch = strbeg + mg->mg_len;        /* Defined pos() */
            if (prog->reganch & ROPT_ANCH_GPOS) {
-               if (s > PL_reg_ganch)
+               if (s > reginfo.ganch)
                    goto phooey;
-               s = PL_reg_ganch;
+               s = reginfo.ganch;
            }
        }
        else                            /* pos() not defined */
-           PL_reg_ganch = strbeg;
+           reginfo.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;
@@ -1762,7 +1727,7 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
     /* Simplest case:  anchored match need be tried only once. */
     /*  [unless only anchor is BOL and multiline is set] */
     if (prog->reganch & (ROPT_ANCH & ~ROPT_ANCH_GPOS)) {
-       if (s == startpos && regtry(prog, startpos))
+       if (s == startpos && regtry(&reginfo, startpos))
            goto got_it;
        else if (multiline || (prog->reganch & ROPT_IMPLICIT)
                 || (prog->reganch & ROPT_ANCH_MBOL)) /* XXXX SBOL? */
@@ -1777,7 +1742,7 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
                if (s == startpos)
                    goto after_try;
                while (1) {
-                   if (regtry(prog, s))
+                   if (regtry(&reginfo, s))
                        goto got_it;
                  after_try:
                    if (s >= end)
@@ -1795,7 +1760,7 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
                    s--;
                while (s < end) {
                    if (*s++ == '\n') { /* don't need PL_utf8skip here */
-                       if (regtry(prog, s))
+                       if (regtry(&reginfo, s))
                            goto got_it;
                    }
                }               
@@ -1803,7 +1768,7 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
        }
        goto phooey;
     } else if (prog->reganch & ROPT_ANCH_GPOS) {
-       if (regtry(prog, PL_reg_ganch))
+       if (regtry(&reginfo, reginfo.ganch))
            goto got_it;
        goto phooey;
     }
@@ -1824,7 +1789,7 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
            while (s < strend) {
                if (*s == ch) {
                    DEBUG_EXECUTE_r( did_match = 1 );
-                   if (regtry(prog, s)) goto got_it;
+                   if (regtry(&reginfo, s)) goto got_it;
                    s += UTF8SKIP(s);
                    while (s < strend && *s == ch)
                        s += UTF8SKIP(s);
@@ -1836,7 +1801,7 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
            while (s < strend) {
                if (*s == ch) {
                    DEBUG_EXECUTE_r( did_match = 1 );
-                   if (regtry(prog, s)) goto got_it;
+                   if (regtry(&reginfo, s)) goto got_it;
                    s++;
                    while (s < strend && *s == ch)
                        s++;
@@ -1849,9 +1814,9 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
                                   "Did not find anchored character...\n")
                );
     }
-    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;
@@ -1907,21 +1872,21 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
                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) {
-                   if (regtry(prog, s))
+                   if (regtry(&reginfo, s))
                        goto got_it;
                    s += UTF8SKIP(s);
                }
            }
            else {
                while (s <= last1) {
-                   if (regtry(prog, s))
+                   if (regtry(&reginfo, s))
                        goto got_it;
                    s++;
                }
@@ -1953,7 +1918,7 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
            int len0;
            int len1;
 
-           regprop(prop, c);
+           regprop(prog, prop, c);
            s0 = UTF ?
              pv_uni_display(dsv0, (U8*)SvPVX_const(prop), SvCUR(prop), 60,
                             UNI_DISPLAY_REGEX) :
@@ -1967,13 +1932,13 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
                          len0, len0, s0,
                          len1, len1, s1);
        });
-        if (find_byclass(prog, c, s, strend, 0))
+        if (find_byclass(prog, c, s, strend, &reginfo))
            goto got_it;
        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;
@@ -2000,7 +1965,7 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
                        last = strend - len + 1;
                    else if (!multiline)
                        last = memEQ(strend - len, little, len)
-                           ? strend - len : Nullch;
+                           ? strend - len : NULL;
                    else
                        goto find_last;
                } else {
@@ -2025,7 +1990,7 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
        /* We don't know much -- general case. */
        if (do_utf8) {
            for (;;) {
-               if (regtry(prog, s))
+               if (regtry(&reginfo, s))
                    goto got_it;
                if (s >= strend)
                    break;
@@ -2034,7 +1999,7 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
        }
        else {
            do {
-               if (regtry(prog, s))
+               if (regtry(&reginfo, s))
                    goto got_it;
            } while (s++ < strend);
        }
@@ -2052,7 +2017,7 @@ got_it:
            sv_setsv(oreplsv, GvSV(PL_replgv));/* So that when GvSV(replgv) is
                                                  restored, the value remains
                                                  the same. */
-       restore_pos(aTHX_ 0);
+       restore_pos(aTHX_ prog);
     }
 
     /* make sure $`, $&, $', and $digit will work later */
@@ -2092,7 +2057,7 @@ phooey:
     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);
+       restore_pos(aTHX_ prog);
     return 0;
 }
 
@@ -2100,12 +2065,13 @@ phooey:
  - regtry - try match at specific point
  */
 STATIC I32                     /* 0 failure, 1 success */
-S_regtry(pTHX_ regexp *prog, char *startpos)
+S_regtry(pTHX_ const regmatch_info *reginfo, char *startpos)
 {
-    register I32 i;
+    dVAR;
     register I32 *sp;
     register I32 *ep;
     CHECKPOINT lastcp;
+    regexp *prog = reginfo->prog;
     GET_RE_DEBUG_FLAGS_DECL;
 
 #ifdef DEBUGGING
@@ -2127,24 +2093,27 @@ S_regtry(pTHX_ regexp *prog, char *startpos)
        /* SAVEI8(cxstack[cxstack_ix].blk_gimme);
           cxstack[cxstack_ix].blk_gimme = G_SCALAR; */
 
-       if (PL_reg_sv) {
+       if (reginfo->sv) {
            /* Make $_ available to executed code. */
-           if (PL_reg_sv != DEFSV) {
+           if (reginfo->sv != DEFSV) {
                SAVE_DEFSV;
-               DEFSV = PL_reg_sv;
+               DEFSV = reginfo->sv;
            }
        
-           if (!(SvTYPE(PL_reg_sv) >= SVt_PVMG && SvMAGIC(PL_reg_sv)
-                 && (mg = mg_find(PL_reg_sv, PERL_MAGIC_regex_global)))) {
+           if (!(SvTYPE(reginfo->sv) >= SVt_PVMG && SvMAGIC(reginfo->sv)
+                 && (mg = mg_find(reginfo->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(reginfo->sv, (SV*)0, PERL_MAGIC_regex_global,
+                                &PL_vtbl_mglob, NULL, 0);
                mg->mg_len = -1;
            }
            PL_reg_magic    = mg;
            PL_reg_oldpos   = mg->mg_len;
-           SAVEDESTRUCTOR_X(restore_pos, 0);
+           SAVEDESTRUCTOR_X(restore_pos, prog);
         }
         if (!PL_reg_curpm) {
            Newxz(PL_reg_curpm, 1, PMOP);
@@ -2174,7 +2143,7 @@ S_regtry(pTHX_ regexp *prog, char *startpos)
            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 */
     }
@@ -2214,6 +2183,7 @@ S_regtry(pTHX_ regexp *prog, char *startpos)
     sp = prog->startp;
     ep = prog->endp;
     if (prog->nparens) {
+       register I32 i;
        for (i = prog->nparens; i > (I32)*PL_reglastparen; i--) {
            *++sp = -1;
            *++ep = -1;
@@ -2221,7 +2191,7 @@ S_regtry(pTHX_ regexp *prog, char *startpos)
     }
 #endif
     REGCP_SET(lastcp);
-    if (regmatch(prog->program + 1)) {
+    if (regmatch(reginfo, prog->program + 1)) {
        prog->endp[0] = PL_reginput - PL_bostr;
        return 1;
     }
@@ -2248,6 +2218,7 @@ typedef struct {
     regnode *next;
     char *locinput;
     I32 nextchr;
+    int minmod;
 #ifdef DEBUGGING
     int regindent;
 #endif
@@ -2272,7 +2243,7 @@ typedef union re_unwind_t {
 #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 (cache_offset | cache_bit) { \
+    if (st->u.whilem.cache_offset | st->u.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))) { \
@@ -2282,13 +2253,13 @@ typedef union re_unwind_t {
                    "%*s  (remove success from failure cache)\n", \
                    REPORT_CODE_OFF+PL_regindent*2, "") \
            ); \
-           PL_reg_poscache[cache_offset] &= ~(1<<cache_bit); \
+           PL_reg_poscache[st->u.whilem.cache_offset] &= ~(1<<st->u.whilem.cache_bit); \
        } \
     } \
     sayYES; \
 } STMT_END
 #define CACHEsayNO STMT_START { \
-    if (cache_offset | cache_bit) { \
+    if (st->u.whilem.cache_offset | st->u.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))) { \
@@ -2298,7 +2269,7 @@ typedef union re_unwind_t {
                    "%*s  (remove failure from success cache)\n", \
                    REPORT_CODE_OFF+PL_regindent*2, "") \
            ); \
-           PL_reg_poscache[cache_offset] &= ~(1<<cache_bit); \
+           PL_reg_poscache[st->u.whilem.cache_offset] &= ~(1<<st->u.whilem.cache_bit); \
        } \
     } \
     sayNO; \
@@ -2316,57 +2287,71 @@ typedef union re_unwind_t {
 /* Make sure there is a test for this +1 options in re_tests */
 #define TRIE_INITAL_ACCEPT_BUFFLEN 4;
 
-#define TRIE_CHECK_STATE_IS_ACCEPTING STMT_START {                       \
-    if ( trie->states[ state ].wordnum ) {                               \
-       if ( !accepted ) {                                               \
-           ENTER;                                                       \
-           SAVETMPS;                                                    \
-           bufflen = TRIE_INITAL_ACCEPT_BUFFLEN ;                       \
-           sv_accept_buff=NEWSV( 1234,                                  \
-             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 );                                \
-           accept_buff = (reg_trie_accepted*)SvPV_nolen( sv_accept_buff );\
-       } else {                                                         \
-           if ( accepted >= bufflen ) {                                 \
-               bufflen *= 2;                                            \
-               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 ) );                         \
-       }                                                                \
-       accept_buff[ accepted ].wordnum = trie->states[ state ].wordnum; \
-       accept_buff[ accepted ].endpos = uc;                             \
-       ++accepted;                                                      \
-    } } STMT_END
-
-#define TRIE_HANDLE_CHAR STMT_START {                                   \
-        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;                                                      \
-    } STMT_END
+#define SLAB_FIRST(s) (&(s)->states[0])
+#define SLAB_LAST(s)  (&(s)->states[PERL_REGMATCH_SLAB_SLOTS-1])
+
+/* 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 SLAB_FIRST(s);
+}
+
+/* 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:
+
+
+/* push a new regex state. Set newst to point to it */
+
+#define PUSH_STATE(newst, resume) \
+    depth++;   \
+    DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "PUSH STATE(%d)\n", depth)); \
+    st->scan = scan;   \
+    st->next = next;   \
+    st->n = n; \
+    st->locinput = locinput;   \
+    st->resume_state = resume; \
+    newst = st+1;   \
+    if (newst >  SLAB_LAST(PL_regmatch_slab)) \
+       newst = S_push_slab(aTHX);  \
+    PL_regmatch_state = newst; \
+    newst->cc = 0;  \
+    newst->minmod = 0; \
+    newst->sw = 0;  \
+    newst->logical = 0;        \
+    newst->unwind = 0; \
+    locinput = PL_reginput; \
+    nextchr = UCHARAT(locinput);    
+
+#define POP_STATE \
+    DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "POP STATE(%d)\n", depth)); \
+    depth--; \
+    st--; \
+    if (st < SLAB_FIRST(PL_regmatch_slab)) { \
+       PL_regmatch_slab = PL_regmatch_slab->prev; \
+       st = SLAB_LAST(PL_regmatch_slab); \
+    } \
+    PL_regmatch_state = st; \
+    scan       = st->scan; \
+    next       = st->next; \
+    n          = st->n; \
+    locinput   = st->locinput; \
+    nextchr = UCHARAT(locinput);
 
 /*
  - regmatch - main matching routine
@@ -2381,57 +2366,165 @@ 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)
+S_regmatch(pTHX_ const regmatch_info *reginfo, regnode *prog)
 {
     dVAR;
-    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 */
-    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;
-
-    /* used by the trie code */
-    SV                 *sv_accept_buff = 0;  /* accepting states we have traversed */
-    reg_trie_accepted  *accept_buff = 0;     /* "" */
-    reg_trie_data      *trie;                /* what trie are we using right now */
-    U32 accepted = 0;                        /* how many accepting states we have seen*/
-
-#if 0
-    I32 firstcp = PL_savestack_ix;
-#endif
     register const 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);
+    const U32 uniflags = UTF8_ALLOW_DEFAULT;
 
-    SV *re_debug_flags = NULL;
-#endif
-    U32 uniflags = ckWARN(WARN_UTF8) ? 0 : UTF8_ALLOW_ANY;
+    regexp *rex = reginfo->prog;
 
-    GET_RE_DEBUG_FLAGS;
+    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;
+
+    /* 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 */
+    regmatch_state *newst;  /* when pushing a state, this is the new one */
+    regmatch_state *yes_state = NULL; /* state to pop to on success of
+                                                           subpattern */
+    
 #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 = SLAB_FIRST(PL_regmatch_slab);
+    }
 
+    /* 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 >  SLAB_LAST(PL_regmatch_slab))
+       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_EXECUTE_r( {
-           SV *prop = sv_newmortal();
+           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);
@@ -2457,21 +2550,22 @@ S_regmatch(pTHX_ regnode *prog)
                pref0_len = 0;
            if (pref0_len > pref_len)
                pref0_len = pref_len;
-           regprop(prop, scan);
+           regprop(rex, prop, scan);
            {
              const char * const s0 =
                do_utf8 && OP(scan) != CANY ?
-               pv_uni_display(dsv0, (U8*)(locinput - pref_len),
+               pv_uni_display(PERL_DEBUG_PAD(0), (U8*)(locinput - pref_len),
                               pref0_len, 60, UNI_DISPLAY_REGEX) :
                locinput - pref_len;
              const int len0 = do_utf8 ? strlen(s0) : pref0_len;
              const char * const s1 = do_utf8 && OP(scan) != CANY ?
-               pv_uni_display(dsv1, (U8*)(locinput - pref_len + pref0_len),
+               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;
              const int len1 = do_utf8 ? strlen(s1) : pref_len - pref0_len;
              const char * const s2 = do_utf8 && OP(scan) != CANY ?
-               pv_uni_display(dsv2, (U8*)locinput,
+               pv_uni_display(PERL_DEBUG_PAD(2), (U8*)locinput,
                               PL_regeol - locinput, 60, UNI_DISPLAY_REGEX) :
                locinput;
              const int len2 = do_utf8 ? strlen(s2) : l;
@@ -2490,7 +2584,7 @@ S_regmatch(pTHX_ regnode *prog)
                            PL_colors[1],
                            15 - l - pref_len + 1,
                            "",
-                           (IV)(scan - PL_regprogram), PL_regindent*2, "",
+                           (IV)(scan - rex->program), PL_regindent*2, "",
                            SvPVX_const(prop));
            }
        });
@@ -2503,7 +2597,7 @@ S_regmatch(pTHX_ regnode *prog)
        case BOL:
            if (locinput == PL_bostr)
            {
-               /* regtill = regbol; */
+               /* reginfo->till = reginfo->bol; */
                break;
            }
            sayNO;
@@ -2519,7 +2613,7 @@ S_regmatch(pTHX_ regnode *prog)
                break;
            sayNO;
        case GPOS:
-           if (locinput == PL_reg_ganch)
+           if (locinput == reginfo->ganch)
                break;
            sayNO;
        case EOL:
@@ -2575,12 +2669,9 @@ S_regmatch(pTHX_ regnode *prog)
           traverse the TRIE keeping track of all accepting states
           we transition through until we get to a failing node.
 
-          we use two slightly different pieces of code to handle
-          the traversal depending on whether its case sensitive or
-          not. we reuse the accept code however. (this should probably
-          be turned into a macro.)
 
        */
+       case TRIE:
        case TRIEF:
        case TRIEFL:
            {
@@ -2593,13 +2684,48 @@ S_regmatch(pTHX_ regnode *prog)
                STRLEN foldlen = 0;
                U8 *uscan = (U8*)NULL;
                STRLEN bufflen=0;
-               accepted = 0;
-
-               trie = (reg_trie_data*)PL_regdata->data[ ARG( scan ) ];
+               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*)rex->data->data[ ARG( scan ) ];
+               st->u.trie.accepted = 0; /* how many accepting states we have seen */
+               result = 0;
 
                while ( state && uc <= (U8*)PL_regeol ) {
 
-                   TRIE_CHECK_STATE_IS_ACCEPTING;
+                   if (trie->states[ state ].wordnum) {
+                       if (!st->u.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->u.trie.accept_buff =
+                               (reg_trie_accepted*)SvPV_nolen(sv_accept_buff );
+                       }
+                       else {
+                           if (st->u.trie.accepted >= bufflen) {
+                               bufflen *= 2;
+                               st->u.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->u.trie.accept_buff[st->u.trie.accepted].wordnum = trie->states[state].wordnum;
+                       st->u.trie.accept_buff[st->u.trie.accepted].endpos = uc;
+                       ++st->u.trie.accepted;
+                   }
 
                    base = trie->states[ state ].trans.base;
 
@@ -2607,12 +2733,12 @@ S_regmatch(pTHX_ regnode *prog)
                                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)accepted );
+                                   (UV)state, (UV)base, (UV)st->u.trie.accepted );
                    );
 
                    if ( base ) {
-
-                       if ( do_utf8 ) {
+                       switch (trie_type) {
+                       case trie_uft8_fold:
                            if ( foldlen>0 ) {
                                uvc = utf8n_to_uvuni( uscan, UTF8_MAXLEN, &len, uniflags );
                                foldlen -= len;
@@ -2625,14 +2751,47 @@ S_regmatch(pTHX_ regnode *prog)
                                foldlen -= UNISKIP( uvc );
                                uscan = foldbuf + UNISKIP( uvc );
                            }
-                       } else {
+                           break;
+                       case trie_utf8:
+                           uvc = utf8n_to_uvuni( (U8*)uc, UTF8_MAXLEN,
+                                                           &len, uniflags );
+                           break;
+                       case trie_plain:
                            uvc = (UV)*uc;
                            len = 1;
                        }
 
-                       TRIE_HANDLE_CHAR;
+                       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 {
+                   }
+                   else {
                        state = 0;
                    }
                    DEBUG_TRIE_EXECUTE_r(
@@ -2641,65 +2800,8 @@ S_regmatch(pTHX_ regnode *prog)
                            charid, uvc, (UV)state, PL_colors[5] );
                    );
                }
-               if ( !accepted ) {
-                  sayNO;
-               } else {
-                   goto TrieAccept;
-               }
-           }
-           /* unreached codepoint: we jump into the middle of the next case
-              from previous if blocks */
-       case TRIE:
-           {
-               U8 *uc = (U8*)locinput;
-               U32 state = 1;
-               U16 charid = 0;
-               U32 base = 0;
-               UV uvc = 0;
-               STRLEN len = 0;
-               STRLEN bufflen = 0;
-               accepted = 0;
-
-               trie = (reg_trie_data*)PL_regdata->data[ ARG( scan ) ];
-
-               while ( state && uc <= (U8*)PL_regeol ) {
-
-                   TRIE_CHECK_STATE_IS_ACCEPTING;
-
-                   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)accepted );
-                   );
-
-                   if ( base ) {
-
-                       if ( do_utf8 ) {
-                           uvc = utf8n_to_uvuni( (U8*)uc, UTF8_MAXLEN, &len, uniflags );
-                       } else {
-                           uvc = (U32)*uc;
-                           len = 1;
-                       }
-
-                        TRIE_HANDLE_CHAR;
-
-                   } 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 ( !accepted ) {
+               if (!st->u.trie.accepted )
                   sayNO;
-               }
-           }
-
 
            /*
               There was at least one accepting state that we
@@ -2713,62 +2815,63 @@ S_regmatch(pTHX_ regnode *prog)
               eventually terminates once all of the accepting states
               have been tried.
            */
-       TrieAccept:
-           {
-               int gotit = 0;
 
-               if ( accepted == 1 ) {
+               if ( st->u.trie.accepted == 1 ) {
                    DEBUG_EXECUTE_r({
-                        SV **tmp = av_fetch( trie->words, accept_buff[ 0 ].wordnum-1, 0 );
+                        SV ** const tmp = av_fetch( trie->words, st->u.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],
-                           accept_buff[ 0 ].wordnum,
+                           st->u.trie.accept_buff[ 0 ].wordnum,
                            tmp ? SvPV_nolen_const( *tmp ) : "not compiled under -Dr",
                            PL_colors[5] );
                    });
-                   PL_reginput = (char *)accept_buff[ 0 ].endpos;
+                   PL_reginput = (char *)st->u.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;
-                   gotit = regmatch( scan + NEXT_OFF( scan ) );
+                   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)accepted,
+                            REPORT_CODE_OFF + PL_regindent * 2, "", PL_colors[4], (IV)st->u.trie.accepted,
                             PL_colors[5] );
                     );
-                   while ( !gotit && accepted-- ) {
+                   while ( !result && st->u.trie.accepted-- ) {
                        U32 best = 0;
                        U32 cur;
-                       for( cur = 1 ; cur <= accepted ; cur++ ) {
+                       for( cur = 1 ; cur <= st->u.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, accept_buff[ best ].wordnum, (IV)cur,
-                                   accept_buff[ cur ].wordnum, PL_colors[5] );
+                                   (IV)best, st->u.trie.accept_buff[ best ].wordnum, (IV)cur,
+                                   st->u.trie.accept_buff[ cur ].wordnum, PL_colors[5] );
                            );
 
-                           if ( accept_buff[ cur ].wordnum < accept_buff[ best ].wordnum )
-                                   best = cur;
+                           if (st->u.trie.accept_buff[cur].wordnum <
+                                   st->u.trie.accept_buff[best].wordnum)
+                               best = cur;
                        }
                        DEBUG_EXECUTE_r({
-                           SV **tmp = av_fetch( trie->words, accept_buff[ best ].wordnum - 1, 0 );
+                           reg_trie_data * const trie = (reg_trie_data*)
+                                           rex->data->data[ARG(scan)];
+                           SV ** const tmp = av_fetch( trie->words, st->u.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],
-                               accept_buff[best].wordnum,
+                               st->u.trie.accept_buff[best].wordnum,
                                tmp ? SvPV_nolen_const( *tmp ) : "not compiled under -Dr",scan,
                                PL_colors[5] );
                        });
-                       if ( best<accepted ) {
-                           reg_trie_accepted tmp = accept_buff[ best ];
-                           accept_buff[ best ] = accept_buff[ accepted ];
-                           accept_buff[ accepted ] = tmp;
-                           best = accepted;
+                       if ( best<st->u.trie.accepted ) {
+                           reg_trie_accepted tmp = st->u.trie.accept_buff[ best ];
+                           st->u.trie.accept_buff[ best ] = st->u.trie.accept_buff[ st->u.trie.accepted ];
+                           st->u.trie.accept_buff[ st->u.trie.accepted ] = tmp;
+                           best = st->u.trie.accepted;
                        }
-                       PL_reginput = (char *)accept_buff[ best ].endpos;
+                       PL_reginput = (char *)st->u.trie.accept_buff[ best ].endpos;
 
                         /* 
                            as far as I can tell we only need the SAVETMPS/FREETMPS 
@@ -2776,27 +2879,28 @@ S_regmatch(pTHX_ regnode *prog)
                            all until I can be sure.
                          */
                        SAVETMPS;
-                       gotit = regmatch( scan + NEXT_OFF( scan ) ) ;
+                       REGMATCH(scan + NEXT_OFF(scan), TRIE2);
+                       /*** all unsaved local vars undefined at this point */
                        FREETMPS;
                    }
                    FREETMPS;
                    LEAVE;
                }
                
-               if ( gotit ) {
+               if (result) {
                    sayYES;
                } else {
                    sayNO;
                }
            }
            /* unreached codepoint */
-       case EXACT:
-           s = STRING(scan);
-           ln = STR_LEN(scan);
+       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;
-               const char *e = s + ln;
+               const char *e = s + st->ln;
 
                if (do_utf8) {
                    /* The target is utf8, the pattern is not utf8. */
@@ -2834,26 +2938,27 @@ 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,
@@ -2861,7 +2966,7 @@ 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 &&
@@ -2880,20 +2985,21 @@ 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;
 
-               if (!reginclass(scan, (U8*)locinput, &inclasslen, do_utf8))
+               if (!reginclass(rex, scan, (U8*)locinput, &inclasslen, do_utf8))
                    sayNO_ANYOF;
                if (locinput >= PL_regeol)
                    sayNO;
@@ -2904,7 +3010,7 @@ S_regmatch(pTHX_ regnode *prog)
            else {
                if (nextchr < 0)
                    nextchr = UCHARAT(locinput);
-               if (!REGINCLASS(scan, (U8*)locinput))
+               if (!REGINCLASS(rex, scan, (U8*)locinput))
                    sayNO_ANYOF;
                if (!nextchr && locinput >= PL_regeol)
                    sayNO;
@@ -2977,35 +3083,35 @@ S_regmatch(pTHX_ regnode *prog)
            /* was last char in word? */
            if (do_utf8) {
                if (locinput == PL_bostr)
-                   ln = '\n';
+                   st->ln = '\n';
                else {
                    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, uniflags);
                }
                if (OP(scan) == BOUND || OP(scan) == NBOUND) {
-                   ln = isALNUM_uni(ln);
+                   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;
@@ -3131,16 +3237,17 @@ 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;
                const char *e = PL_bostr + PL_regendp[n];
@@ -3176,18 +3283,19 @@ 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:
@@ -3196,21 +3304,21 @@ S_regmatch(pTHX_ regnode *prog)
            break;
        case EVAL:
        {
-           dSP;
-           OP_4tree *oop = PL_op;
-           COP *ocurcop = PL_curcop;
-           PAD *old_comppad;
            SV *ret;
-           struct regexp *oreg = PL_reg_re;
-       
-           n = ARG(scan);
-           PL_op = (OP_4tree*)PL_regdata->data[n];
-           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;
+               /* execute the code in the {...} */
+               dSP;
+               SV ** const before = SP;
+               OP_4tree * const oop = PL_op;
+               COP * const ocurcop = PL_curcop;
+               PAD *old_comppad;
+           
+               n = ARG(scan);
+               PL_op = (OP_4tree*)rex->data->data[n];
+               DEBUG_EXECUTE_r( PerlIO_printf(Perl_debug_log, "  re_eval 0x%"UVxf"\n", PTR2UV(PL_op)) );
+               PAD_SAVE_LOCAL(old_comppad, (PAD*)rex->data->data[n + 2]);
+               PL_regendp[0] = PL_reg_magic->mg_len = locinput - PL_bostr;
+
                CALLRUNOPS(aTHX);                       /* Scalar context. */
                SPAGAIN;
                if (SP == before)
@@ -3219,20 +3327,24 @@ S_regmatch(pTHX_ regnode *prog)
                    ret = POPs;
                    PUTBACK;
                }
-           }
 
-           PL_op = oop;
-           PAD_RESTORE_LOCAL(old_comppad);
-           PL_curcop = ocurcop;
-           if (logical) {
-               if (logical == 2) {     /* Postponed subexpression. */
-                   regexp *re;
-                   MAGIC *mg = Null(MAGIC*);
-                   re_cc_state state;
-                   CHECKPOINT cp, lastcp;
-                    int toggleutf;
-                   register SV *sv;
+               PL_op = oop;
+               PAD_RESTORE_LOCAL(old_comppad);
+               PL_curcop = ocurcop;
+               if (!st->logical) {
+                   /* /(?{...})/ */
+                   sv_setsv(save_scalar(PL_replgv), ret);
+                   break;
+               }
+           }
+           if (st->logical == 2) { /* Postponed subexpression: /(??{...})/ */
+               regexp *re;
+               {
+                   /* extract RE object from returned value; compiling if
+                    * necessary */
 
+                   MAGIC *mg = NULL;
+                   SV *sv;
                    if(SvROK(ret) && SvSMAGICAL(sv = SvRV(ret)))
                        mg = mg_find(sv, PERL_MAGIC_qr);
                    else if (SvSMAGICAL(ret)) {
@@ -3248,96 +3360,63 @@ S_regmatch(pTHX_ regnode *prog)
                    }
                    else {
                        STRLEN len;
-                       const char *t = SvPV_const(ret, len);
+                       const char * const t = SvPV_const(ret, len);
                        PMOP pm;
-                       char * const oprecomp = PL_regprecomp;
                        const I32 osize = PL_regsize;
-                       const I32 onpar = PL_regnpar;
 
                        Zero(&pm, 1, PMOP);
-                        if (DO_UTF8(ret)) pm.op_pmdynflags |= PMdf_DYN_UTF8;
+                       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_GMG)))
                            sv_magic(ret,(SV*)ReREFCNT_inc(re),
                                        PERL_MAGIC_qr,0,0);
-                       PL_regprecomp = oprecomp;
                        PL_regsize = osize;
-                       PL_regnpar = onpar;
                    }
-                   DEBUG_EXECUTE_r(
-                       PerlIO_printf(Perl_debug_log,
-                                     "Entering embedded \"%s%.60s%s%s\"\n",
-                                     PL_colors[0],
-                                     re->precomp,
-                                     PL_colors[1],
-                                     (strlen(re->precomp) > 60 ? "..." : ""))
-                       );
-                   state.node = next;
-                   state.prev = PL_reg_call_cc;
-                   state.cc = PL_regcc;
-                   state.re = PL_reg_re;
-
-                   PL_regcc = 0;
-               
-                   cp = regcppush(0);  /* Save *all* the positions. */
-                   REGCP_SET(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;
-
-                   if (regmatch(re->program + 1)) {
-                       /* Even though we succeeded, we need to restore
-                          global variables, since we may be wrapped inside
-                          SUSPEND, thus the match may be not finished yet. */
-
-                       /* XXXX Do this only if SUSPENDed? */
-                       PL_reg_call_cc = state.prev;
-                       PL_regcc = 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);
-                       sayYES;
-                   }
-                   ReREFCNT_dec(re);
-                   REGCP_UNWIND(lastcp);
-                   regcppop();
-                   PL_reg_call_cc = state.prev;
-                   PL_regcc = 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;
-                   sayNO;
                }
-               sw = SvTRUE(ret);
-               logical = 0;
-           }
-           else {
-               sv_setsv(save_scalar(PL_replgv), ret);
-               cache_re(oreg);
+
+               /* run the pattern returned from (??{...}) */
+
+               DEBUG_EXECUTE_r(
+                   PerlIO_printf(Perl_debug_log,
+                                 "Entering embedded \"%s%.60s%s%s\"\n",
+                                 PL_colors[0],
+                                 re->precomp,
+                                 PL_colors[1],
+                                 (strlen(re->precomp) > 60 ? "..." : ""))
+                   );
+
+               st->u.eval.cp = regcppush(0);   /* Save *all* the positions. */
+               REGCP_SET(st->u.eval.lastcp);
+               *PL_reglastparen = 0;
+               *PL_reglastcloseparen = 0;
+               PL_reginput = locinput;
+
+               /* XXXX This is too dramatic a measure... */
+               PL_reg_maxiter = 0;
+
+               st->logical = 0;
+               st->u.eval.toggleutf = ((PL_reg_flags & RF_utf8) != 0) ^
+                           ((re->reganch & ROPT_UTF8) != 0);
+               if (st->u.eval.toggleutf) PL_reg_flags ^= RF_utf8;
+               st->u.eval.prev_rex = rex;
+               rex = re;
+
+               /* resume to current state on success */
+               st->u.yes.prev_yes_state = yes_state;
+               yes_state = st;
+               PUSH_STATE(newst, resume_EVAL);
+               st = newst;
+
+               /* now continue  from first node in postoned RE */
+               next = re->program + 1;
+               break;
+               /* NOTREACHED */
            }
+           /* /(?(?{...})X|Y)/ */
+           st->sw = SvTRUE(ret);
+           st->logical = 0;
            break;
        }
        case OPEN:
@@ -3356,11 +3435,11 @@ 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);
@@ -3369,38 +3448,39 @@ 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.
@@ -3446,35 +3526,40 @@ 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->u.curlyx.cp = PL_savestack_ix;
+               st->u.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->u.curlyx.parenfloor = parenfloor;
+               st->u.curlyx.cur = -1; /* this will be updated by WHILEM */
+               st->u.curlyx.min = ARG1(scan);
+               st->u.curlyx.max  = ARG2(scan);
+               st->u.curlyx.scan = NEXTOPER(scan) + EXTRA_STEP_2ARGS;
+               st->u.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->u.curlyx.cp);
+               st->cc = st->u.curlyx.outercc;
+               saySAME(result);
            }
-           /* NOT REACHED */
+           /* NOTREACHED */
        case WHILEM: {
                /*
                 * This is really hard to understand, because after we match
@@ -3485,50 +3570,54 @@ 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. */
-               I32 cache_offset = 0, cache_bit = 0;
+               st->u.whilem.lastloc = st->cc->u.curlyx.lastloc; /* Detection of 0-len. */
+               st->u.whilem.cache_offset = 0;
+               st->u.whilem.cache_bit = 0;
                
-               n = cc->cur + 1;        /* how many we know we matched */
+               n = st->cc->u.curlyx.cur + 1; /* how many we know we matched */
                PL_reginput = locinput;
 
                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->u.curlyx.min,
+                                 (long)st->cc->u.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;
+               if (locinput == st->cc->u.curlyx.lastloc && n >= st->cc->u.curlyx.min) {
+                   st->u.whilem.savecc = st->cc;
+                   st->cc = st->cc->u.curlyx.outercc;
+                   if (st->cc)
+                       st->ln = st->cc->u.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->u.whilem.savecc->next, WHILEM1);
+                   /*** all unsaved local vars undefined at this point */
+                   st->cc = st->u.whilem.savecc;
+                   if (result)
                        sayYES;
-                   if (PL_regcc)
-                       PL_regcc->cur = ln;
-                   PL_regcc = cc;
+                   if (st->cc->u.curlyx.outercc)
+                       st->cc->u.curlyx.outercc->u.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->u.curlyx.min) {
+                   st->cc->u.curlyx.cur = n;
+                   st->cc->u.curlyx.lastloc = locinput;
+                   REGMATCH(st->cc->u.curlyx.scan, WHILEM2);
+                   /*** all unsaved local vars undefined at this point */
+                   if (result)
                        sayYES;
-                   cc->cur = n - 1;
-                   cc->lastloc = lastloc;
+                   st->cc->u.curlyx.cur = n - 1;
+                   st->cc->u.curlyx.lastloc = st->u.whilem.lastloc;
                    sayNO;
                }
 
@@ -3560,13 +3649,13 @@ S_regmatch(pTHX_ regnode *prog)
                        );
                }
                if (PL_reg_leftiter < 0) {
-                   cache_offset = locinput - PL_bostr;
+                   st->u.whilem.cache_offset = locinput - PL_bostr;
 
-                   cache_offset = (scan->flags & 0xf) - 1 + POSCACHE_START
-                           + cache_offset * (scan->flags>>4);
-                   cache_bit = cache_offset % 8;
-                   cache_offset /= 8;
-                   if (PL_reg_poscache[cache_offset] & (1<<cache_bit)) {
+                   st->u.whilem.cache_offset = (scan->flags & 0xf) - 1 + POSCACHE_START
+                           + st->u.whilem.cache_offset * (scan->flags>>4);
+                   st->u.whilem.cache_bit = st->u.whilem.cache_offset % 8;
+                   st->u.whilem.cache_offset /= 8;
+                   if (PL_reg_poscache[st->u.whilem.cache_offset] & (1<<st->u.whilem.cache_bit)) {
                    DEBUG_EXECUTE_r(
                        PerlIO_printf(Perl_debug_log,
                                      "%*s  already tried at this position...\n",
@@ -3579,29 +3668,32 @@ S_regmatch(pTHX_ regnode *prog)
                            /* cache records failure */
                            sayNO_SILENT;
                    }
-                   PL_reg_poscache[cache_offset] |= (1<<cache_bit);
+                   PL_reg_poscache[st->u.whilem.cache_offset] |= (1<<st->u.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);
+               if (st->cc->minmod) {
+                   st->u.whilem.savecc = st->cc;
+                   st->cc = st->cc->u.curlyx.outercc;
+                   if (st->cc)
+                       st->ln = st->cc->u.curlyx.cur;
+                   st->u.whilem.cp = regcppush(st->u.whilem.savecc->u.curlyx.parenfloor);
+                   REGCP_SET(st->u.whilem.lastcp);
+                   REGMATCH(st->u.whilem.savecc->next, WHILEM3);
+                   /*** all unsaved local vars undefined at this point */
+                   st->cc = st->u.whilem.savecc;
+                   if (result) {
+                       regcpblow(st->u.whilem.cp);
                        CACHEsayYES;    /* All done. */
                    }
-                   REGCP_UNWIND(lastcp);
-                   regcppop();
-                   if (PL_regcc)
-                       PL_regcc->cur = ln;
-                   PL_regcc = cc;
+                   REGCP_UNWIND(st->u.whilem.lastcp);
+                   regcppop(rex);
+                   if (st->cc->u.curlyx.outercc)
+                       st->cc->u.curlyx.outercc->u.curlyx.cur = st->ln;
 
-                   if (n >= cc->max) { /* Maximum greed exceeded? */
+                   if (n >= st->cc->u.curlyx.max) { /* Maximum greed exceeded? */
                        if (ckWARN(WARN_REGEXP) && n >= REG_INFTY
                            && !(PL_reg_flags & RF_warned)) {
                            PL_reg_flags |= RF_warned;
@@ -3619,34 +3711,38 @@ S_regmatch(pTHX_ regnode *prog)
                        );
                    /* 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);
+                   st->cc->u.curlyx.cur = n;
+                   st->cc->u.curlyx.lastloc = locinput;
+                   st->u.whilem.cp = regcppush(st->cc->u.curlyx.parenfloor);
+                   REGCP_SET(st->u.whilem.lastcp);
+                   REGMATCH(st->cc->u.curlyx.scan, WHILEM4);
+                   /*** all unsaved local vars undefined at this point */
+                   if (result) {
+                       regcpblow(st->u.whilem.cp);
                        CACHEsayYES;
                    }
-                   REGCP_UNWIND(lastcp);
-                   regcppop();
-                   cc->cur = n - 1;
-                   cc->lastloc = lastloc;
+                   REGCP_UNWIND(st->u.whilem.lastcp);
+                   regcppop(rex);
+                   st->cc->u.curlyx.cur = n - 1;
+                   st->cc->u.curlyx.lastloc = st->u.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);
+               if (n < st->cc->u.curlyx.max) { /* More greed allowed? */
+                   st->u.whilem.cp = regcppush(st->cc->u.curlyx.parenfloor);
+                   st->cc->u.curlyx.cur = n;
+                   st->cc->u.curlyx.lastloc = locinput;
+                   REGCP_SET(st->u.whilem.lastcp);
+                   REGMATCH(st->cc->u.curlyx.scan, WHILEM5);
+                   /*** all unsaved local vars undefined at this point */
+                   if (result) {
+                       regcpblow(st->u.whilem.cp);
                        CACHEsayYES;
                    }
-                   REGCP_UNWIND(lastcp);
-                   regcppop();         /* Restore some previous $<digit>s? */
+                   REGCP_UNWIND(st->u.whilem.lastcp);
+                   regcppop(rex);      /* Restore some previous $<digit>s? */
                    PL_reginput = locinput;
                    DEBUG_EXECUTE_r(
                        PerlIO_printf(Perl_debug_log,
@@ -3663,19 +3759,22 @@ 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))
+               st->u.whilem.savecc = st->cc;
+               st->cc = st->cc->u.curlyx.outercc;
+               if (st->cc)
+                   st->ln = st->cc->u.curlyx.cur;
+               REGMATCH(st->u.whilem.savecc->next, WHILEM6);
+               /*** all unsaved local vars undefined at this point */
+               st->cc = st->u.whilem.savecc;
+               if (result)
                    CACHEsayYES;
-               if (PL_regcc)
-                   PL_regcc->cur = ln;
-               PL_regcc = cc;
-               cc->cur = n - 1;
-               cc->lastloc = lastloc;
+               if (st->cc->u.curlyx.outercc)
+                   st->cc->u.curlyx.outercc->u.curlyx.cur = st->ln;
+               st->cc->u.curlyx.cur = n - 1;
+               st->cc->u.curlyx.lastloc = st->u.whilem.lastloc;
                CACHEsayNO;
            }
-           /* NOT REACHED */
+           /* NOTREACHED */
        case BRANCHJ:
            next = scan + ARG(scan);
            if (next == scan)
@@ -3686,26 +3785,26 @@ 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 (!next || OP(next) != type)  /* No choice. */
                    next = inner;       /* Avoid recursion. */
                else {
                    const I32 lastparen = *PL_reglastparen;
-                   I32 unwind1;
-                   re_unwind_branch_t *uw;
-
                    /* 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;
                    uw->next = next;
                    uw->locinput = locinput;
                    uw->nextchr = nextchr;
+                   uw->minmod = st->minmod;
 #ifdef DEBUGGING
                    uw->regindent = ++PL_regindent;
 #endif
@@ -3718,81 +3817,113 @@ S_regmatch(pTHX_ regnode *prog)
            }
            break;
        case MINMOD:
-           minmod = 1;
+           st->minmod = 1;
            break;
        case CURLYM:
        {
-           I32 l = 0;
-           CHECKPOINT lastcp;
+           st->u.curlym.l = st->u.curlym.matches = 0;
        
            /* We suppose that the next guy does not need
               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->u.curlym.paren = scan->flags;
+           if (st->u.curlym.paren) {
+               if (st->u.curlym.paren > PL_regsize)
+                   PL_regsize = st->u.curlym.paren;
+               if (st->u.curlym.paren > (I32)*PL_reglastparen)
+                   *PL_reglastparen = st->u.curlym.paren;
            }
            scan = NEXTOPER(scan) + NODE_STEP_REGNODE;
-           if (paren)
+           if (st->u.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->u.curlym.maxwanted = st->minmod ? st->ln : n;
+           if (st->u.curlym.maxwanted) {
+               while (PL_reginput < PL_regeol && st->u.curlym.matches < st->u.curlym.maxwanted) {
+                   REGMATCH(scan, CURLYM1);
+                   /*** all unsaved local vars undefined at this point */
+                   if (!result)
+                       break;
+                   /* on first match, determine length, u.curlym.l */
+                   if (!st->u.curlym.matches++) {
+                       if (PL_reg_match_utf8) {
+                           char *s = locinput;
+                           while (s < PL_reginput) {
+                               st->u.curlym.l++;
+                               s += UTF8SKIP(s);
+                           }
+                       }
+                       else {
+                           st->u.curlym.l = PL_reginput - locinput;
+                       }
+                       if (st->u.curlym.l == 0) {
+                           st->u.curlym.matches = st->u.curlym.maxwanted;
+                           break;
+                       }
+                   }
+                   locinput = PL_reginput;
+               }
+           }
+
+           PL_reginput = locinput;
+
+           if (st->minmod) {
+               st->minmod = 0;
+               if (st->ln && st->u.curlym.matches < st->ln)
                    sayNO;
-               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->u.curlym.c1 = st->u.curlym.c2 = -1000;
                    else {
                        if (PL_regkind[(U8)OP(text_node)] == REF) {
-                           c1 = c2 = -1000;
+                           st->u.curlym.c1 = st->u.curlym.c2 = -1000;
                            goto assume_ok_MM;
                        }
-                       else { c1 = (U8)*STRING(text_node); }
+                       else { st->u.curlym.c1 = (U8)*STRING(text_node); }
                        if (OP(text_node) == EXACTF || OP(text_node) == REFF)
-                           c2 = PL_fold[c1];
+                           st->u.curlym.c2 = PL_fold[st->u.curlym.c1];
                        else if (OP(text_node) == EXACTFL || OP(text_node) == REFFL)
-                           c2 = PL_fold_locale[c1];
+                           st->u.curlym.c2 = PL_fold_locale[st->u.curlym.c1];
                        else
-                           c2 = c1;
+                           st->u.curlym.c2 = st->u.curlym.c1;
                    }
                }
                else
-                   c1 = c2 = -1000;
+                   st->u.curlym.c1 = st->u.curlym.c2 = -1000;
            assume_ok_MM:
-               REGCP_SET(lastcp);
-               while (n >= ln || (n == REG_INFTY && ln > 0)) { /* ln overflow ? */
+               REGCP_SET(st->u.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->u.curlym.c1 == -1000 ||
+                       UCHARAT(PL_reginput) == st->u.curlym.c1 ||
+                       UCHARAT(PL_reginput) == st->u.curlym.c2)
                    {
-                       if (paren) {
-                           if (ln) {
-                               PL_regstartp[paren] =
-                                   HOPc(PL_reginput, -l) - PL_bostr;
-                               PL_regendp[paren] = PL_reginput - PL_bostr;
+                       if (st->u.curlym.paren) {
+                           if (st->ln) {
+                               PL_regstartp[st->u.curlym.paren] =
+                                   HOPc(PL_reginput, -st->u.curlym.l) - PL_bostr;
+                               PL_regendp[st->u.curlym.paren] = PL_reginput - PL_bostr;
                            }
                            else
-                               PL_regendp[paren] = -1;
+                               PL_regendp[st->u.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->u.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
@@ -3800,100 +3931,103 @@ S_regmatch(pTHX_ regnode *prog)
                }
            }
            else {
-               n = regrepeat_hard(scan, n, &l);
-               locinput = PL_reginput;
                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->u.curlym.matches, (IV)st->u.curlym.l)
                    );
-               if (n >= ln) {
+               if (st->u.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->u.curlym.c1 = st->u.curlym.c2 = -1000;
                        else {
                            if (PL_regkind[(U8)OP(text_node)] == REF) {
-                               c1 = c2 = -1000;
+                               st->u.curlym.c1 = st->u.curlym.c2 = -1000;
                                goto assume_ok_REG;
                            }
-                           else { c1 = (U8)*STRING(text_node); }
+                           else { st->u.curlym.c1 = (U8)*STRING(text_node); }
 
                            if (OP(text_node) == EXACTF || OP(text_node) == REFF)
-                               c2 = PL_fold[c1];
+                               st->u.curlym.c2 = PL_fold[st->u.curlym.c1];
                            else if (OP(text_node) == EXACTFL || OP(text_node) == REFFL)
-                               c2 = PL_fold_locale[c1];
+                               st->u.curlym.c2 = PL_fold_locale[st->u.curlym.c1];
                            else
-                               c2 = c1;
+                               st->u.curlym.c2 = st->u.curlym.c1;
                        }
                    }
                    else
-                       c1 = c2 = -1000;
+                       st->u.curlym.c1 = st->u.curlym.c2 = -1000;
                }
            assume_ok_REG:
-               REGCP_SET(lastcp);
-               while (n >= ln) {
+               REGCP_SET(st->u.curlym.lastcp);
+               while (st->u.curlym.matches >= st->ln) {
                    /* If it could work, try it. */
-                   if (c1 == -1000 ||
-                       UCHARAT(PL_reginput) == c1 ||
-                       UCHARAT(PL_reginput) == c2)
+                   if (st->u.curlym.c1 == -1000 ||
+                       UCHARAT(PL_reginput) == st->u.curlym.c1 ||
+                       UCHARAT(PL_reginput) == st->u.curlym.c2)
                    {
                        DEBUG_EXECUTE_r(
-                               PerlIO_printf(Perl_debug_log,
-                                             "%*s  trying tail with n=%"IVdf"...\n",
-                                             (int)(REPORT_CODE_OFF+PL_regindent*2), "", (IV)n)
+                           PerlIO_printf(Perl_debug_log,
+                               "%*s  trying tail with matches=%"IVdf"...\n",
+                               (int)(REPORT_CODE_OFF+PL_regindent*2),
+                               "", (IV)st->u.curlym.matches)
                            );
-                       if (paren) {
-                           if (n) {
-                               PL_regstartp[paren] = HOPc(PL_reginput, -l) - PL_bostr;
-                               PL_regendp[paren] = PL_reginput - PL_bostr;
+                       if (st->u.curlym.paren) {
+                           if (st->u.curlym.matches) {
+                               PL_regstartp[st->u.curlym.paren]
+                                   = HOPc(PL_reginput, -st->u.curlym.l) - PL_bostr;
+                               PL_regendp[st->u.curlym.paren] = PL_reginput - PL_bostr;
                            }
                            else
-                               PL_regendp[paren] = -1;
+                               PL_regendp[st->u.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->u.curlym.lastcp);
                    }
                    /* Couldn't or didn't -- back up. */
-                   n--;
-                   locinput = HOPc(locinput, -l);
+                   st->u.curlym.matches--;
+                   locinput = HOPc(locinput, -st->u.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->u.plus.paren = scan->flags;     /* Which paren to set */
+           if (st->u.plus.paren > PL_regsize)
+               PL_regsize = st->u.plus.paren;
+           if (st->u.plus.paren > (I32)*PL_reglastparen)
+               *PL_reglastparen = st->u.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->u.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->u.plus.paren = 0;
            goto repeat;
        case PLUS:
-           ln = 1;
+           st->ln = 1;
            n = REG_INFTY;
            scan = NEXTOPER(scan);
-           paren = 0;
+           st->u.plus.paren = 0;
          repeat:
            /*
            * Lookahead to avoid useless match attempts
@@ -3912,20 +4046,20 @@ 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->u.plus.c1 = st->u.plus.c2 = -1000;
                else {
                    if (PL_regkind[(U8)OP(text_node)] == REF) {
-                       c1 = c2 = -1000;
+                       st->u.plus.c1 = st->u.plus.c2 = -1000;
                        goto assume_ok_easy;
                    }
                    else { s = (U8*)STRING(text_node); }
 
                    if (!UTF) {
-                       c2 = c1 = *s;
+                       st->u.plus.c2 = st->u.plus.c1 = *s;
                        if (OP(text_node) == EXACTF || OP(text_node) == REFF)
-                           c2 = PL_fold[c1];
+                           st->u.plus.c2 = PL_fold[st->u.plus.c1];
                        else if (OP(text_node) == EXACTFL || OP(text_node) == REFFL)
-                           c2 = PL_fold_locale[c1];
+                           st->u.plus.c2 = PL_fold_locale[st->u.plus.c1];
                    }
                    else { /* UTF */
                        if (OP(text_node) == EXACTF || OP(text_node) == REFF) {
@@ -3936,118 +4070,117 @@ S_regmatch(pTHX_ regnode *prog)
                             to_utf8_lower((U8*)s, tmpbuf1, &ulen1);
                             to_utf8_upper((U8*)s, tmpbuf2, &ulen2);
 
-                            c1 = utf8n_to_uvuni(tmpbuf1, UTF8_MAXBYTES, 0,
+                            st->u.plus.c1 = utf8n_to_uvuni(tmpbuf1, UTF8_MAXBYTES, 0,
                                                 uniflags);
-                            c2 = utf8n_to_uvuni(tmpbuf2, UTF8_MAXBYTES, 0,
+                            st->u.plus.c2 = utf8n_to_uvuni(tmpbuf2, UTF8_MAXBYTES, 0,
                                                 uniflags);
                        }
                        else {
-                           c2 = c1 = utf8n_to_uvchr(s, UTF8_MAXBYTES, 0,
+                           st->u.plus.c2 = st->u.plus.c1 = utf8n_to_uvchr(s, UTF8_MAXBYTES, 0,
                                                     uniflags);
                        }
                    }
                }
            }
            else
-               c1 = c2 = -1000;
+               st->u.plus.c1 = st->u.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(rex, 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->u.plus.lastcp);
+               if (st->u.plus.c1 != -1000) {
+                   st->u.plus.old = locinput;
+                   st->u.plus.count = 0;
 
                    if  (n == REG_INFTY) {
-                       e = PL_regeol - 1;
+                       st->u.plus.e = PL_regeol - 1;
                        if (do_utf8)
-                           while (UTF8_IS_CONTINUATION(*(U8*)e))
-                               e--;
+                           while (UTF8_IS_CONTINUATION(*(U8*)st->u.plus.e))
+                               st->u.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->u.plus.e = locinput;
+                            m >0 && st->u.plus.e + UTF8SKIP(st->u.plus.e) <= PL_regeol; m--)
+                           st->u.plus.e += UTF8SKIP(st->u.plus.e);
                    }
                    else {
-                       e = locinput + n - ln;
-                       if (e >= PL_regeol)
-                           e = PL_regeol - 1;
+                       st->u.plus.e = locinput + n - st->ln;
+                       if (st->u.plus.e >= PL_regeol)
+                           st->u.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->u.plus.c1 == st->u.plus.c2) {
+                               while (locinput <= st->u.plus.e &&
+                                      UCHARAT(locinput) != st->u.plus.c1)
                                    locinput++;
                            } else {
-                               while (locinput <= e
-                                      && UCHARAT(locinput) != c1
-                                      && UCHARAT(locinput) != c2)
+                               while (locinput <= st->u.plus.e
+                                      && UCHARAT(locinput) != st->u.plus.c1
+                                      && UCHARAT(locinput) != st->u.plus.c2)
                                    locinput++;
                            }
-                           count = locinput - old;
+                           st->u.plus.count = locinput - st->u.plus.old;
                        }
                        else {
-                           if (c1 == c2) {
+                           if (st->u.plus.c1 == st->u.plus.c2) {
                                STRLEN len;
                                /* count initialised to
                                 * utf8_distance(old, locinput) */
-                               while (locinput <= e &&
+                               while (locinput <= st->u.plus.e &&
                                       utf8n_to_uvchr((U8*)locinput,
                                                      UTF8_MAXBYTES, &len,
-                                                     uniflags) != (UV)c1) {
+                                                     uniflags) != (UV)st->u.plus.c1) {
                                    locinput += len;
-                                   count++;
+                                   st->u.plus.count++;
                                }
                            } else {
                                STRLEN len;
                                /* count initialised to
                                 * utf8_distance(old, locinput) */
-                               while (locinput <= e) {
+                               while (locinput <= st->u.plus.e) {
                                    UV c = utf8n_to_uvchr((U8*)locinput,
                                                          UTF8_MAXBYTES, &len,
                                                          uniflags);
-                                   if (c == (UV)c1 || c == (UV)c2)
+                                   if (c == (UV)st->u.plus.c1 || c == (UV)st->u.plus.c2)
                                        break;
                                    locinput += len;
-                                   count++;
+                                   st->u.plus.count++;
                                }
                            }
                        }
-                       if (locinput > e)
+                       if (locinput > st->u.plus.e)
                            sayNO;
                        /* PL_reginput == old now */
-                       if (locinput != old) {
-                           ln = 1;     /* Did some */
-                           if (regrepeat(scan, count) < count)
+                       if (locinput != st->u.plus.old) {
+                           st->ln = 1; /* Did some */
+                           if (regrepeat(rex, scan, st->u.plus.count) < st->u.plus.count)
                                sayNO;
                        }
                        /* PL_reginput == locinput now */
-                       TRYPAREN(paren, ln, locinput);
+                       TRYPAREN(st->u.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->u.plus.lastcp);
                        /* Couldn't or didn't -- move forward. */
-                       old = locinput;
+                       st->u.plus.old = locinput;
                        if (do_utf8)
                            locinput += UTF8SKIP(locinput);
                        else
                            locinput++;
-                       count = 1;
+                       st->u.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->u.plus.c1 != -1000) {
                        if (do_utf8)
                            c = utf8n_to_uvchr((U8*)PL_reginput,
                                               UTF8_MAXBYTES, 0,
@@ -4055,22 +4188,24 @@ S_regmatch(pTHX_ regnode *prog)
                        else
                            c = UCHARAT(PL_reginput);
                        /* If it could work, try it. */
-                       if (c == (UV)c1 || c == (UV)c2)
+                       if (c == (UV)st->u.plus.c1 || c == (UV)st->u.plus.c2)
                        {
-                           TRYPAREN(paren, ln, PL_reginput);
-                           REGCP_UNWIND(lastcp);
+                           TRYPAREN(st->u.plus.paren, st->ln, PL_reginput, PLUS2);
+                           /*** all unsaved local vars undefined at this point */
+                           REGCP_UNWIND(st->u.plus.lastcp);
                        }
                    }
                    /* If it could work, try it. */
-                   else if (c1 == -1000)
+                   else if (st->u.plus.c1 == -1000)
                    {
-                       TRYPAREN(paren, ln, PL_reginput);
-                       REGCP_UNWIND(lastcp);
+                       TRYPAREN(st->u.plus.paren, st->ln, PL_reginput, PLUS3);
+                       /*** all unsaved local vars undefined at this point */
+                       REGCP_UNWIND(st->u.plus.lastcp);
                    }
                    /* Couldn't or didn't -- move forward. */
                    PL_reginput = locinput;
-                   if (regrepeat(scan, 1)) {
-                       ln++;
+                   if (regrepeat(rex, scan, 1)) {
+                       st->ln++;
                        locinput = PL_reginput;
                    }
                    else
@@ -4078,47 +4213,24 @@ S_regmatch(pTHX_ regnode *prog)
                }
            }
            else {
-               CHECKPOINT lastcp;
-               n = regrepeat(scan, n);
+               n = regrepeat(rex, scan, n);
                locinput = PL_reginput;
-               if (ln < n && PL_regkind[(U8)OP(next)] == EOL &&
+               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--;
+                       st->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_MAXBYTES, 0,
-                                                  uniflags);
-                           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);
-                   }
-               }
-               else {
+               REGCP_SET(st->u.plus.lastcp);
+               {
                    UV c = 0;
-                   while (n >= ln) {
-                       if (c1 != -1000) {
+                   while (n >= st->ln) {
+                       if (st->u.plus.c1 != -1000) {
                            if (do_utf8)
                                c = utf8n_to_uvchr((U8*)PL_reginput,
                                                   UTF8_MAXBYTES, 0,
@@ -4127,10 +4239,11 @@ S_regmatch(pTHX_ regnode *prog)
                                c = UCHARAT(PL_reginput);
                        }
                        /* If it could work, try it. */
-                       if (c1 == -1000 || c == (UV)c1 || c == (UV)c2)
+                       if (st->u.plus.c1 == -1000 || c == (UV)st->u.plus.c1 || c == (UV)st->u.plus.c2)
                            {
-                               TRYPAREN(paren, n, PL_reginput);
-                               REGCP_UNWIND(lastcp);
+                               TRYPAREN(st->u.plus.paren, n, PL_reginput, PLUS4);
+                               /*** all unsaved local vars undefined at this point */
+                               REGCP_UNWIND(st->u.plus.lastcp);
                            }
                        /* Couldn't or didn't -- back up. */
                        n--;
@@ -4141,46 +4254,12 @@ S_regmatch(pTHX_ regnode *prog)
            sayNO;
            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. */
-               cache_re(PL_reg_call_cc->re);
-               PL_regcc = 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);
-                   sayYES;
-               }
-               REGCP_UNWIND(lastcp);
-               regcppop();
-               PL_reg_call_cc = cur_call_cc;
-               PL_regcc = cctmp;
-               PL_reg_re = re;
-               cache_re(re);
-
-               DEBUG_EXECUTE_r(
-                   PerlIO_printf(Perl_debug_log,
-                                 "%*s  continuation failed...\n",
-                                 REPORT_CODE_OFF+PL_regindent*2, "")
-                   );
-               sayNO_SILENT;
-           }
-           if (locinput < PL_regtill) {
+           if (locinput < reginfo->till) {
                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),
-                                     (long)(PL_regtill - PL_reg_starttry),
+                                     (long)(reginfo->till - PL_reg_starttry),
                                      PL_colors[5]));
                sayNO_FINAL;            /* Cannot match: too short. */
            }
@@ -4196,7 +4275,7 @@ 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;
@@ -4207,7 +4286,7 @@ 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;
@@ -4216,21 +4295,22 @@ 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;
@@ -4248,10 +4328,49 @@ 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 >  SLAB_LAST(PL_regmatch_slab))
+               st = S_push_slab(aTHX);
+           PL_regmatch_state = st;
+
+           oldst->next = next;
+           oldst->n = n;
+           oldst->locinput = locinput;
+
+           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
+       }
     }
 
+
+
     /*
     * We get here only if there's trouble -- normally "case END" is
     * the terminating point.
@@ -4268,6 +4387,52 @@ yes_loud:
        );
     goto yes;
 yes_final:
+
+    if (yes_state) {
+       /* we have successfully completed a subexpression, but we must now
+        * pop to the state marked by yes_state and continue from there */
+
+       assert(st != yes_state);
+       while (yes_state < SLAB_FIRST(PL_regmatch_slab)
+           || yes_state > SLAB_LAST(PL_regmatch_slab))
+       {
+           /* not in this slab, pop slab */
+           depth -= (st - SLAB_FIRST(PL_regmatch_slab) + 1);
+           PL_regmatch_slab = PL_regmatch_slab->prev;
+           st = SLAB_LAST(PL_regmatch_slab);
+       }
+       depth -= (st - yes_state);
+       DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "POP STATE TO (%d)\n", depth)); \
+       st = yes_state;
+       yes_state = st->u.yes.prev_yes_state;
+       PL_regmatch_state = st;
+
+       switch (st->resume_state) {
+       case resume_EVAL:
+           if (st->u.eval.toggleutf)
+               PL_reg_flags ^= RF_utf8;
+           ReREFCNT_dec(rex);
+           rex = st->u.eval.prev_rex;
+           /* XXXX This is too dramatic a measure... */
+           PL_reg_maxiter = 0;
+           /* Restore parens of the caller without popping the
+            * savestack */
+           {
+               I32 tmp = PL_savestack_ix;
+               PL_savestack_ix = st->u.eval.lastcp;
+               regcppop(rex);
+               PL_savestack_ix = tmp;
+           }
+           PL_reginput = locinput;
+            /* continue at the node following the (??{...}) */
+           next        = st->next;
+           goto reenter;
+
+       default:
+           Perl_croak(aTHX_ "unexpected yes reume state");
+       }
+    }
+
     DEBUG_EXECUTE_r(PerlIO_printf(Perl_debug_log, "%sMatch successful!%s\n",
                          PL_colors[4], PL_colors[5]));
 yes:
@@ -4275,11 +4440,58 @@ yes:
     PL_regindent--;
 #endif
 
-#if 0                                  /* Breaks $^R */
-    if (unwind)
-       regcpblow(firstcp);
-#endif
-    return 1;
+    result = 1;
+    /* XXX this is duplicate(ish) code to that in the do_no section.
+     * eventually a yes should just pop the stack back to the current
+     * yes_state */
+    if (depth) {
+       /* restore previous state and re-enter */
+       POP_STATE;
+
+       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_EVAL:
+       default:
+           Perl_croak(aTHX_ "regexp resume memory corruption");
+       }
+    }
+    goto final_exit;
 
 no:
     DEBUG_EXECUTE_r(
@@ -4290,14 +4502,14 @@ no:
     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);
+           re_unwind_branch_t * const uwb = &(uw->branch);
            const I32 lastparen = uwb->lastparen;
        
            REGCP_UNWIND(uwb->lastcp);
@@ -4305,10 +4517,11 @@ do_no:
                PL_regendp[n] = -1;
            *PL_reglastparen = n;
            scan = next = uwb->next;
+           st->minmod = uwb->minmod;
            if ( !scan ||
                 OP(scan) != (uwb->type == RE_UNWIND_BRANCH
                              ? BRANCH : BRANCHJ) ) {           /* Failure */
-               unwind = uwb->prev;
+               st->unwind = uwb->prev;
 #ifdef DEBUGGING
                PL_regindent--;
 #endif
@@ -4332,16 +4545,99 @@ 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;
+
+    if (depth) {
+       /* there's a previous state to backtrack to */
+       POP_STATE;
+       switch (st->resume_state) {
+       case resume_TRIE1:
+           goto resume_point_TRIE1;
+       case resume_TRIE2:
+           goto resume_point_TRIE2;
+       case resume_EVAL:
+           /* we have failed an (??{...}). Restore state to the outer re
+            * then re-throw the failure */
+           if (st->u.eval.toggleutf)
+               PL_reg_flags ^= RF_utf8;
+           ReREFCNT_dec(rex);
+           rex = st->u.eval.prev_rex;
+           yes_state = st->u.yes.prev_yes_state;
+
+           /* XXXX This is too dramatic a measure... */
+           PL_reg_maxiter = 0;
+
+           PL_reginput = locinput;
+           REGCP_UNWIND(st->u.eval.lastcp);
+           regcppop(rex);
+           goto do_no;
+
+       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;
+       default:
+           Perl_croak(aTHX_ "regexp resume memory corruption");
+       }
+    }
+
+final_exit:
+
+    /* 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;
+           Safefree(osl);
+       }
+    }
+
+    return result;
+
 }
 
 /*
@@ -4353,7 +4649,7 @@ do_no:
  * rather than incrementing count on every character.  [Er, except utf8.]]
  */
 STATIC I32
-S_regrepeat(pTHX_ const regnode *p, I32 max)
+S_regrepeat(pTHX_ const regexp *prog, const regnode *p, I32 max)
 {
     dVAR;
     register char *scan;
@@ -4366,7 +4662,7 @@ S_regrepeat(pTHX_ const regnode *p, I32 max)
     if (max == REG_INFTY)
        max = I32_MAX;
     else if (max < loceol - scan)
-      loceol = scan + max;
+       loceol = scan + max;
     switch (OP(p)) {
     case REG_ANY:
        if (do_utf8) {
@@ -4416,12 +4712,12 @@ S_regrepeat(pTHX_ const regnode *p, I32 max)
        if (do_utf8) {
            loceol = PL_regeol;
            while (hardcount < max && scan < loceol &&
-                  reginclass(p, (U8*)scan, 0, do_utf8)) {
+                  reginclass(prog, p, (U8*)scan, 0, do_utf8)) {
                scan += UTF8SKIP(scan);
                hardcount++;
            }
        } else {
-           while (scan < loceol && REGINCLASS(p, (U8*)scan))
+           while (scan < loceol && REGINCLASS(prog, p, (U8*)scan))
                scan++;
        }
        break;
@@ -4579,10 +4875,10 @@ S_regrepeat(pTHX_ const regnode *p, I32 max)
 
     DEBUG_r({
                SV *re_debug_flags = NULL;
-               SV *prop = sv_newmortal();
+               SV * const prop = sv_newmortal();
                 GET_RE_DEBUG_FLAGS;
                 DEBUG_EXECUTE_r({
-               regprop(prop, p);
+               regprop(prog, prop, p);
                PerlIO_printf(Perl_debug_log,
                              "%*s  %s can match %"IVdf" times out of %"IVdf"...\n",
                              REPORT_CODE_OFF+1, "", SvPVX_const(prop),(IV)c,(IV)max);
@@ -4592,74 +4888,25 @@ S_regrepeat(pTHX_ const regnode *p, I32 max)
     return(c);
 }
 
-/*
- - regrepeat_hard - repeatedly match something, report total lenth and length
- *
- * The repeater is supposed to have constant non-zero 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 const regnode* node, bool doinit, SV** listsvp, SV **altsvp)
+Perl_regclass_swash(pTHX_ const regexp *prog, register const regnode* node, bool doinit, SV** listsvp, SV **altsvp)
 {
+    dVAR;
     SV *sw  = NULL;
     SV *si  = NULL;
     SV *alt = NULL;
+    const struct reg_data *data = prog ? prog->data : NULL;
 
-    if (PL_regdata && PL_regdata->count) {
+    if (data && data->count) {
        const U32 n = ARG(node);
 
-       if (PL_regdata->what[n] == 's') {
-           SV * const rv = (SV*)PL_regdata->data[n];
+       if (data->what[n] == 's') {
+           SV * const rv = (SV*)data->data[n];
            AV * const av = (AV*)SvRV((SV*)rv);
            SV **const ary = AvARRAY(av);
            SV **a, **b;
@@ -4701,7 +4948,7 @@ Perl_regclass_swash(pTHX_ register const regnode* node, bool doinit, SV** listsv
  */
 
 STATIC bool
-S_reginclass(pTHX_ register const regnode *n, register const U8* p, STRLEN* lenp, register bool do_utf8)
+S_reginclass(pTHX_ const regexp *prog, register const regnode *n, register const U8* p, STRLEN* lenp, register bool do_utf8)
 {
     dVAR;
     const char flags = ANYOF_FLAGS(n);
@@ -4712,8 +4959,8 @@ S_reginclass(pTHX_ register const regnode *n, register const U8* p, STRLEN* lenp
 
     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);
+               (UTF8_ALLOW_DEFAULT & UTF8_ALLOW_ANYUV) | UTF8_CHECK_ONLY);
+               /* see [perl #37836] for UTF8_ALLOW_ANYUV */
        if (len == (STRLEN)-1)
            Perl_croak(aTHX_ "Malformed UTF-8 character (fatal)");
     }
@@ -4730,7 +4977,7 @@ S_reginclass(pTHX_ register const regnode *n, register const U8* p, STRLEN* lenp
            match = TRUE;
        if (!match) {
            AV *av;
-           SV * const sw = regclass_swash(n, TRUE, 0, (SV**)&av);
+           SV * const sw = regclass_swash(prog, n, TRUE, 0, (SV**)&av);
        
            if (sw) {
                if (swash_fetch(sw, p, do_utf8))
@@ -4824,14 +5071,9 @@ S_reginclass(pTHX_ register const regnode *n, register const U8* p, STRLEN* lenp
 }
 
 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 */
@@ -4854,14 +5096,9 @@ 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 */
@@ -4892,15 +5129,16 @@ S_reghopmaybe3(pTHX_ U8* s, I32 off, U8* lim)
 static void
 restore_pos(pTHX_ void *arg)
 {
-    PERL_UNUSED_ARG(arg);
+    dVAR;
+    regexp * const rex = (regexp *)arg;
     if (PL_reg_eval_set) {
        if (PL_reg_oldsaved) {
-           PL_reg_re->subbeg = PL_reg_oldsaved;
-           PL_reg_re->sublen = PL_reg_oldsavedlen;
+           rex->subbeg = PL_reg_oldsaved;
+           rex->sublen = PL_reg_oldsavedlen;
 #ifdef PERL_OLD_COPY_ON_WRITE
-           PL_reg_re->saved_copy = PL_nrs;
+           rex->saved_copy = PL_nrs;
 #endif
-           RX_MATCH_COPIED_on(PL_reg_re);
+           RX_MATCH_COPIED_on(rex);
        }
        PL_reg_magic->mg_len = PL_reg_oldpos;
        PL_reg_eval_set = 0;
@@ -4912,8 +5150,8 @@ STATIC void
 S_to_utf8_substr(pTHX_ register regexp *prog)
 {
     if (prog->float_substr && !prog->float_utf8) {
-       SV* sv;
-       prog->float_utf8 = sv = newSVsv(prog->float_substr);
+       SV* const sv = newSVsv(prog->float_substr);
+       prog->float_utf8 = sv;
        sv_utf8_upgrade(sv);
        if (SvTAIL(prog->float_substr))
            SvTAIL_on(sv);
@@ -4921,8 +5159,8 @@ S_to_utf8_substr(pTHX_ register regexp *prog)
            prog->check_utf8 = sv;
     }
     if (prog->anchored_substr && !prog->anchored_utf8) {
-       SV* sv;
-       prog->anchored_utf8 = sv = newSVsv(prog->anchored_substr);
+       SV* const sv = newSVsv(prog->anchored_substr);
+       prog->anchored_utf8 = sv;
        sv_utf8_upgrade(sv);
        if (SvTAIL(prog->anchored_substr))
            SvTAIL_on(sv);
@@ -4934,9 +5172,10 @@ S_to_utf8_substr(pTHX_ register regexp *prog)
 STATIC void
 S_to_byte_substr(pTHX_ register regexp *prog)
 {
+    dVAR;
     if (prog->float_utf8 && !prog->float_substr) {
-       SV* sv;
-       prog->float_substr = sv = newSVsv(prog->float_utf8);
+       SV* sv = newSVsv(prog->float_utf8);
+       prog->float_substr = sv;
        if (sv_utf8_downgrade(sv, TRUE)) {
            if (SvTAIL(prog->float_utf8))
                SvTAIL_on(sv);
@@ -4948,8 +5187,8 @@ S_to_byte_substr(pTHX_ register regexp *prog)
            prog->check_substr = sv;
     }
     if (prog->anchored_utf8 && !prog->anchored_substr) {
-       SV* sv;
-       prog->anchored_substr = sv = newSVsv(prog->anchored_utf8);
+       SV* sv = newSVsv(prog->anchored_utf8);
+       prog->anchored_substr = sv;
        if (sv_utf8_downgrade(sv, TRUE)) {
            if (SvTAIL(prog->anchored_utf8))
                SvTAIL_on(sv);