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[perl5.git] / regcomp.c

/*    regcomp.c
 */

/*
 * "A fair jaw-cracker dwarf-language must be."  --Samwise Gamgee
 */

/* This file contains functions for compiling a regular expression.  See
 * also regexec.c which funnily enough, contains functions for executing
 * a regular expression.
 *
 * This file is also copied at build time to ext/re/re_comp.c, where
 * it's built with -DPERL_EXT_RE_BUILD -DPERL_EXT_RE_DEBUG -DPERL_EXT.
 * This causes the main functions to be compiled under new names and with
 * debugging support added, which makes "use re 'debug'" work.
 */

/* NOTE: this is derived from Henry Spencer's regexp code, and should not
 * confused with the original package (see point 3 below).  Thanks, Henry!
 */

/* Additional note: this code is very heavily munged from Henry's version
 * in places.  In some spots I've traded clarity for efficiency, so don't
 * blame Henry for some of the lack of readability.
 */

/* The names of the functions have been changed from regcomp and
 * regexec to  pregcomp and pregexec in order to avoid conflicts
 * with the POSIX routines of the same names.
*/

#ifdef PERL_EXT_RE_BUILD
/* need to replace pregcomp et al, so enable that */
#  ifndef PERL_IN_XSUB_RE
#    define PERL_IN_XSUB_RE
#  endif
/* need access to debugger hooks */
#  if defined(PERL_EXT_RE_DEBUG) && !defined(DEBUGGING)
#    define DEBUGGING
#  endif
#endif

#ifdef PERL_IN_XSUB_RE
/* We *really* need to overwrite these symbols: */
#  define Perl_pregcomp my_regcomp
#  define Perl_regdump my_regdump
#  define Perl_regprop my_regprop
#  define Perl_pregfree my_regfree
#  define Perl_re_intuit_string my_re_intuit_string
/* *These* symbols are masked to allow static link. */
#  define Perl_regnext my_regnext
#  define Perl_save_re_context my_save_re_context
#  define Perl_reginitcolors my_reginitcolors

#  define PERL_NO_GET_CONTEXT
#endif

/*
 * pregcomp and pregexec -- regsub and regerror are not used in perl
 *
 *      Copyright (c) 1986 by University of Toronto.
 *      Written by Henry Spencer.  Not derived from licensed software.
 *
 *      Permission is granted to anyone to use this software for any
 *      purpose on any computer system, and to redistribute it freely,
 *      subject to the following restrictions:
 *
 *      1. The author is not responsible for the consequences of use of
 *              this software, no matter how awful, even if they arise
 *              from defects in it.
 *
 *      2. The origin of this software must not be misrepresented, either
 *              by explicit claim or by omission.
 *
 *      3. Altered versions must be plainly marked as such, and must not
 *              be misrepresented as being the original software.
 *
 *
 ****    Alterations to Henry's code are...
 ****
 ****    Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
 ****    2000, 2001, 2002, 2003, 2004, 2005, 2006, by Larry Wall and others
 ****
 ****    You may distribute under the terms of either the GNU General Public
 ****    License or the Artistic License, as specified in the README file.

 *
 * Beware that some of this code is subtly aware of the way operator
 * precedence is structured in regular expressions.  Serious changes in
 * regular-expression syntax might require a total rethink.
 */
#include "EXTERN.h"
#define PERL_IN_REGCOMP_C
#include "perl.h"

#ifndef PERL_IN_XSUB_RE
#  include "INTERN.h"
#endif

#define REG_COMP_C
#include "regcomp.h"

#ifdef op
#undef op
#endif /* op */

#ifdef MSDOS
#  if defined(BUGGY_MSC6)
 /* MSC 6.00A breaks on op/regexp.t test 85 unless we turn this off */
#    pragma optimize("a",off)
 /* But MSC 6.00A is happy with 'w', for aliases only across function calls*/
#    pragma optimize("w",on )
#  endif /* BUGGY_MSC6 */
#endif /* MSDOS */

#ifndef STATIC
#define STATIC  static
#endif

typedef struct RExC_state_t {
    U32         flags;                  /* are we folding, multilining? */
    char        *precomp;               /* uncompiled string. */
    regexp      *rx;
    char        *start;                 /* Start of input for compile */
    char        *end;                   /* End of input for compile */
    char        *parse;                 /* Input-scan pointer. */
    I32         whilem_seen;            /* number of WHILEM in this expr */
    regnode     *emit_start;            /* Start of emitted-code area */
    regnode     *emit;                  /* Code-emit pointer; &regdummy = don't = compiling */
    I32         naughty;                /* How bad is this pattern? */
    I32         sawback;                /* Did we see \1, ...? */
    U32         seen;
    I32         size;                   /* Code size. */
    I32         npar;                   /* () count. */
    I32         extralen;
    I32         seen_zerolen;
    I32         seen_evals;
    I32         utf8;
#if ADD_TO_REGEXEC
    char        *starttry;              /* -Dr: where regtry was called. */
#define RExC_starttry   (pRExC_state->starttry)
#endif
} RExC_state_t;

#define RExC_flags      (pRExC_state->flags)
#define RExC_precomp    (pRExC_state->precomp)
#define RExC_rx         (pRExC_state->rx)
#define RExC_start      (pRExC_state->start)
#define RExC_end        (pRExC_state->end)
#define RExC_parse      (pRExC_state->parse)
#define RExC_whilem_seen        (pRExC_state->whilem_seen)
#define RExC_offsets    (pRExC_state->rx->offsets) /* I am not like the others */
#define RExC_emit       (pRExC_state->emit)
#define RExC_emit_start (pRExC_state->emit_start)
#define RExC_naughty    (pRExC_state->naughty)
#define RExC_sawback    (pRExC_state->sawback)
#define RExC_seen       (pRExC_state->seen)
#define RExC_size       (pRExC_state->size)
#define RExC_npar       (pRExC_state->npar)
#define RExC_extralen   (pRExC_state->extralen)
#define RExC_seen_zerolen       (pRExC_state->seen_zerolen)
#define RExC_seen_evals (pRExC_state->seen_evals)
#define RExC_utf8       (pRExC_state->utf8)

#define ISMULT1(c)      ((c) == '*' || (c) == '+' || (c) == '?')
#define ISMULT2(s)      ((*s) == '*' || (*s) == '+' || (*s) == '?' || \
        ((*s) == '{' && regcurly(s)))

#ifdef SPSTART
#undef SPSTART          /* dratted cpp namespace... */
#endif
/*
 * Flags to be passed up and down.
 */
#define WORST           0       /* Worst case. */
#define HASWIDTH        0x1     /* Known to match non-null strings. */
#define SIMPLE          0x2     /* Simple enough to be STAR/PLUS operand. */
#define SPSTART         0x4     /* Starts with * or +. */
#define TRYAGAIN        0x8     /* Weeded out a declaration. */

/* Length of a variant. */

typedef struct scan_data_t {
    I32 len_min;
    I32 len_delta;
    I32 pos_min;
    I32 pos_delta;
    SV *last_found;
    I32 last_end;                       /* min value, <0 unless valid. */
    I32 last_start_min;
    I32 last_start_max;
    SV **longest;                       /* Either &l_fixed, or &l_float. */
    SV *longest_fixed;
    I32 offset_fixed;
    SV *longest_float;
    I32 offset_float_min;
    I32 offset_float_max;
    I32 flags;
    I32 whilem_c;
    I32 *last_closep;
    struct regnode_charclass_class *start_class;
} scan_data_t;

/*
 * Forward declarations for pregcomp()'s friends.
 */

static const scan_data_t zero_scan_data =
  { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};

#define SF_BEFORE_EOL           (SF_BEFORE_SEOL|SF_BEFORE_MEOL)
#define SF_BEFORE_SEOL          0x1
#define SF_BEFORE_MEOL          0x2
#define SF_FIX_BEFORE_EOL       (SF_FIX_BEFORE_SEOL|SF_FIX_BEFORE_MEOL)
#define SF_FL_BEFORE_EOL        (SF_FL_BEFORE_SEOL|SF_FL_BEFORE_MEOL)

#ifdef NO_UNARY_PLUS
#  define SF_FIX_SHIFT_EOL      (0+2)
#  define SF_FL_SHIFT_EOL               (0+4)
#else
#  define SF_FIX_SHIFT_EOL      (+2)
#  define SF_FL_SHIFT_EOL               (+4)
#endif

#define SF_FIX_BEFORE_SEOL      (SF_BEFORE_SEOL << SF_FIX_SHIFT_EOL)
#define SF_FIX_BEFORE_MEOL      (SF_BEFORE_MEOL << SF_FIX_SHIFT_EOL)

#define SF_FL_BEFORE_SEOL       (SF_BEFORE_SEOL << SF_FL_SHIFT_EOL)
#define SF_FL_BEFORE_MEOL       (SF_BEFORE_MEOL << SF_FL_SHIFT_EOL) /* 0x20 */
#define SF_IS_INF               0x40
#define SF_HAS_PAR              0x80
#define SF_IN_PAR               0x100
#define SF_HAS_EVAL             0x200
#define SCF_DO_SUBSTR           0x400
#define SCF_DO_STCLASS_AND      0x0800
#define SCF_DO_STCLASS_OR       0x1000
#define SCF_DO_STCLASS          (SCF_DO_STCLASS_AND|SCF_DO_STCLASS_OR)
#define SCF_WHILEM_VISITED_POS  0x2000

#define UTF (RExC_utf8 != 0)
#define LOC ((RExC_flags & PMf_LOCALE) != 0)
#define FOLD ((RExC_flags & PMf_FOLD) != 0)

#define OOB_UNICODE             12345678
#define OOB_NAMEDCLASS          -1

#define CHR_SVLEN(sv) (UTF ? sv_len_utf8(sv) : SvCUR(sv))
#define CHR_DIST(a,b) (UTF ? utf8_distance(a,b) : a - b)


/* length of regex to show in messages that don't mark a position within */
#define RegexLengthToShowInErrorMessages 127

/*
 * If MARKER[12] are adjusted, be sure to adjust the constants at the top
 * of t/op/regmesg.t, the tests in t/op/re_tests, and those in
 * op/pragma/warn/regcomp.
 */
#define MARKER1 "<-- HERE"    /* marker as it appears in the description */
#define MARKER2 " <-- HERE "  /* marker as it appears within the regex */

#define REPORT_LOCATION " in regex; marked by " MARKER1 " in m/%.*s" MARKER2 "%s/"

/*
 * Calls SAVEDESTRUCTOR_X if needed, then calls Perl_croak with the given
 * arg. Show regex, up to a maximum length. If it's too long, chop and add
 * "...".
 */
#define FAIL(msg) STMT_START {                                          \
    const char *ellipses = "";                                          \
    IV len = RExC_end - RExC_precomp;                                   \
                                                                        \
    if (!SIZE_ONLY)                                                     \
        SAVEDESTRUCTOR_X(clear_re,(void*)RExC_rx);                      \
    if (len > RegexLengthToShowInErrorMessages) {                       \
        /* chop 10 shorter than the max, to ensure meaning of "..." */  \
        len = RegexLengthToShowInErrorMessages - 10;                    \
        ellipses = "...";                                               \
    }                                                                   \
    Perl_croak(aTHX_ "%s in regex m/%.*s%s/",                           \
            msg, (int)len, RExC_precomp, ellipses);                     \
} STMT_END

/*
 * Simple_vFAIL -- like FAIL, but marks the current location in the scan
 */
#define Simple_vFAIL(m) STMT_START {                                    \
    const IV offset = RExC_parse - RExC_precomp;                        \
    Perl_croak(aTHX_ "%s" REPORT_LOCATION,                              \
            m, (int)offset, RExC_precomp, RExC_precomp + offset);       \
} STMT_END

/*
 * Calls SAVEDESTRUCTOR_X if needed, then Simple_vFAIL()
 */
#define vFAIL(m) STMT_START {                           \
    if (!SIZE_ONLY)                                     \
        SAVEDESTRUCTOR_X(clear_re,(void*)RExC_rx);      \
    Simple_vFAIL(m);                                    \
} STMT_END

/*
 * Like Simple_vFAIL(), but accepts two arguments.
 */
#define Simple_vFAIL2(m,a1) STMT_START {                        \
    const IV offset = RExC_parse - RExC_precomp;                        \
    S_re_croak2(aTHX_ m, REPORT_LOCATION, a1,                   \
            (int)offset, RExC_precomp, RExC_precomp + offset);  \
} STMT_END

/*
 * Calls SAVEDESTRUCTOR_X if needed, then Simple_vFAIL2().
 */
#define vFAIL2(m,a1) STMT_START {                       \
    if (!SIZE_ONLY)                                     \
        SAVEDESTRUCTOR_X(clear_re,(void*)RExC_rx);      \
    Simple_vFAIL2(m, a1);                               \
} STMT_END


/*
 * Like Simple_vFAIL(), but accepts three arguments.
 */
#define Simple_vFAIL3(m, a1, a2) STMT_START {                   \
    const IV offset = RExC_parse - RExC_precomp;                \
    S_re_croak2(aTHX_ m, REPORT_LOCATION, a1, a2,               \
            (int)offset, RExC_precomp, RExC_precomp + offset);  \
} STMT_END

/*
 * Calls SAVEDESTRUCTOR_X if needed, then Simple_vFAIL3().
 */
#define vFAIL3(m,a1,a2) STMT_START {                    \
    if (!SIZE_ONLY)                                     \
        SAVEDESTRUCTOR_X(clear_re,(void*)RExC_rx);      \
    Simple_vFAIL3(m, a1, a2);                           \
} STMT_END

/*
 * Like Simple_vFAIL(), but accepts four arguments.
 */
#define Simple_vFAIL4(m, a1, a2, a3) STMT_START {               \
    const IV offset = RExC_parse - RExC_precomp;                \
    S_re_croak2(aTHX_ m, REPORT_LOCATION, a1, a2, a3,           \
            (int)offset, RExC_precomp, RExC_precomp + offset);  \
} STMT_END

#define vWARN(loc,m) STMT_START {                                       \
    const IV offset = loc - RExC_precomp;                               \
    Perl_warner(aTHX_ packWARN(WARN_REGEXP), "%s" REPORT_LOCATION,      \
            m, (int)offset, RExC_precomp, RExC_precomp + offset);       \
} STMT_END

#define vWARNdep(loc,m) STMT_START {                                    \
    const IV offset = loc - RExC_precomp;                               \
    Perl_warner(aTHX_ packWARN2(WARN_DEPRECATED, WARN_REGEXP),          \
            "%s" REPORT_LOCATION,                                       \
            m, (int)offset, RExC_precomp, RExC_precomp + offset);       \
} STMT_END


#define vWARN2(loc, m, a1) STMT_START {                                 \
    const IV offset = loc - RExC_precomp;                               \
    Perl_warner(aTHX_ packWARN(WARN_REGEXP), m REPORT_LOCATION,         \
            a1, (int)offset, RExC_precomp, RExC_precomp + offset);      \
} STMT_END

#define vWARN3(loc, m, a1, a2) STMT_START {                             \
    const IV offset = loc - RExC_precomp;                               \
    Perl_warner(aTHX_ packWARN(WARN_REGEXP), m REPORT_LOCATION,         \
            a1, a2, (int)offset, RExC_precomp, RExC_precomp + offset);  \
} STMT_END

#define vWARN4(loc, m, a1, a2, a3) STMT_START {                         \
    const IV offset = loc - RExC_precomp;                               \
    Perl_warner(aTHX_ packWARN(WARN_REGEXP), m REPORT_LOCATION,         \
            a1, a2, a3, (int)offset, RExC_precomp, RExC_precomp + offset); \
} STMT_END

#define vWARN5(loc, m, a1, a2, a3, a4) STMT_START {                     \
    const IV offset = loc - RExC_precomp;                               \
    Perl_warner(aTHX_ packWARN(WARN_REGEXP), m REPORT_LOCATION,         \
            a1, a2, a3, a4, (int)offset, RExC_precomp, RExC_precomp + offset); \
} STMT_END


/* Allow for side effects in s */
#define REGC(c,s) STMT_START {                  \
    if (!SIZE_ONLY) *(s) = (c); else (void)(s); \
} STMT_END

/* Macros for recording node offsets.   20001227 mjd@plover.com 
 * Nodes are numbered 1, 2, 3, 4.  Node #n's position is recorded in
 * element 2*n-1 of the array.  Element #2n holds the byte length node #n.
 * Element 0 holds the number n.
 */

#define MJD_OFFSET_DEBUG(x)
/* #define MJD_OFFSET_DEBUG(x) Perl_warn_nocontext x */


#define Set_Node_Offset_To_R(node,byte) STMT_START {                    \
    if (! SIZE_ONLY) {                                                  \
        MJD_OFFSET_DEBUG(("** (%d) offset of node %d is %d.\n",         \
                __LINE__, (node), (byte)));                             \
        if((node) < 0) {                                                \
            Perl_croak(aTHX_ "value of node is %d in Offset macro", (int)(node)); \
        } else {                                                        \
            RExC_offsets[2*(node)-1] = (byte);                          \
        }                                                               \
    }                                                                   \
} STMT_END

#define Set_Node_Offset(node,byte) \
    Set_Node_Offset_To_R((node)-RExC_emit_start, (byte)-RExC_start)
#define Set_Cur_Node_Offset Set_Node_Offset(RExC_emit, RExC_parse)

#define Set_Node_Length_To_R(node,len) STMT_START {                     \
    if (! SIZE_ONLY) {                                                  \
        MJD_OFFSET_DEBUG(("** (%d) size of node %d is %d.\n",           \
                __LINE__, (int)(node), (int)(len)));                    \
        if((node) < 0) {                                                \
            Perl_croak(aTHX_ "value of node is %d in Length macro", (int)(node)); \
        } else {                                                        \
            RExC_offsets[2*(node)] = (len);                             \
        }                                                               \
    }                                                                   \
} STMT_END

#define Set_Node_Length(node,len) \
    Set_Node_Length_To_R((node)-RExC_emit_start, len)
#define Set_Cur_Node_Length(len) Set_Node_Length(RExC_emit, len)
#define Set_Node_Cur_Length(node) \
    Set_Node_Length(node, RExC_parse - parse_start)

/* Get offsets and lengths */
#define Node_Offset(n) (RExC_offsets[2*((n)-RExC_emit_start)-1])
#define Node_Length(n) (RExC_offsets[2*((n)-RExC_emit_start)])

static void clear_re(pTHX_ void *r);

/* Mark that we cannot extend a found fixed substring at this point.
   Updata the longest found anchored substring and the longest found
   floating substrings if needed. */

STATIC void
S_scan_commit(pTHX_ const RExC_state_t *pRExC_state, scan_data_t *data)
{
    const STRLEN l = CHR_SVLEN(data->last_found);
    const STRLEN old_l = CHR_SVLEN(*data->longest);

    if ((l >= old_l) && ((l > old_l) || (data->flags & SF_BEFORE_EOL))) {
        SvSetMagicSV(*data->longest, data->last_found);
        if (*data->longest == data->longest_fixed) {
            data->offset_fixed = l ? data->last_start_min : data->pos_min;
            if (data->flags & SF_BEFORE_EOL)
                data->flags
                    |= ((data->flags & SF_BEFORE_EOL) << SF_FIX_SHIFT_EOL);
            else
                data->flags &= ~SF_FIX_BEFORE_EOL;
        }
        else {
            data->offset_float_min = l ? data->last_start_min : data->pos_min;
            data->offset_float_max = (l
                                      ? data->last_start_max
                                      : data->pos_min + data->pos_delta);
            if ((U32)data->offset_float_max > (U32)I32_MAX)
                data->offset_float_max = I32_MAX;
            if (data->flags & SF_BEFORE_EOL)
                data->flags
                    |= ((data->flags & SF_BEFORE_EOL) << SF_FL_SHIFT_EOL);
            else
                data->flags &= ~SF_FL_BEFORE_EOL;
        }
    }
    SvCUR_set(data->last_found, 0);
    {
        SV * const sv = data->last_found;
        if (SvUTF8(sv) && SvMAGICAL(sv)) {
            MAGIC * const mg = mg_find(sv, PERL_MAGIC_utf8);
            if (mg)
                mg->mg_len = 0;
        }
    }
    data->last_end = -1;
    data->flags &= ~SF_BEFORE_EOL;
}

/* Can match anything (initialization) */
STATIC void
S_cl_anything(const RExC_state_t *pRExC_state, struct regnode_charclass_class *cl)
{
    ANYOF_CLASS_ZERO(cl);
    ANYOF_BITMAP_SETALL(cl);
    cl->flags = ANYOF_EOS|ANYOF_UNICODE_ALL;
    if (LOC)
        cl->flags |= ANYOF_LOCALE;
}

/* Can match anything (initialization) */
STATIC int
S_cl_is_anything(const struct regnode_charclass_class *cl)
{
    int value;

    for (value = 0; value <= ANYOF_MAX; value += 2)
        if (ANYOF_CLASS_TEST(cl, value) && ANYOF_CLASS_TEST(cl, value + 1))
            return 1;
    if (!(cl->flags & ANYOF_UNICODE_ALL))
        return 0;
    if (!ANYOF_BITMAP_TESTALLSET((const void*)cl))
        return 0;
    return 1;
}

/* Can match anything (initialization) */
STATIC void
S_cl_init(const RExC_state_t *pRExC_state, struct regnode_charclass_class *cl)
{
    Zero(cl, 1, struct regnode_charclass_class);
    cl->type = ANYOF;
    cl_anything(pRExC_state, cl);
}

STATIC void
S_cl_init_zero(const RExC_state_t *pRExC_state, struct regnode_charclass_class *cl)
{
    Zero(cl, 1, struct regnode_charclass_class);
    cl->type = ANYOF;
    cl_anything(pRExC_state, cl);
    if (LOC)
        cl->flags |= ANYOF_LOCALE;
}

/* 'And' a given class with another one.  Can create false positives */
/* We assume that cl is not inverted */
STATIC void
S_cl_and(struct regnode_charclass_class *cl,
        const struct regnode_charclass_class *and_with)
{
    if (!(and_with->flags & ANYOF_CLASS)
        && !(cl->flags & ANYOF_CLASS)
        && (and_with->flags & ANYOF_LOCALE) == (cl->flags & ANYOF_LOCALE)
        && !(and_with->flags & ANYOF_FOLD)
        && !(cl->flags & ANYOF_FOLD)) {
        int i;

        if (and_with->flags & ANYOF_INVERT)
            for (i = 0; i < ANYOF_BITMAP_SIZE; i++)
                cl->bitmap[i] &= ~and_with->bitmap[i];
        else
            for (i = 0; i < ANYOF_BITMAP_SIZE; i++)
                cl->bitmap[i] &= and_with->bitmap[i];
    } /* XXXX: logic is complicated otherwise, leave it along for a moment. */
    if (!(and_with->flags & ANYOF_EOS))
        cl->flags &= ~ANYOF_EOS;

    if (cl->flags & ANYOF_UNICODE_ALL && and_with->flags & ANYOF_UNICODE &&
        !(and_with->flags & ANYOF_INVERT)) {
        cl->flags &= ~ANYOF_UNICODE_ALL;
        cl->flags |= ANYOF_UNICODE;
        ARG_SET(cl, ARG(and_with));
    }
    if (!(and_with->flags & ANYOF_UNICODE_ALL) &&
        !(and_with->flags & ANYOF_INVERT))
        cl->flags &= ~ANYOF_UNICODE_ALL;
    if (!(and_with->flags & (ANYOF_UNICODE|ANYOF_UNICODE_ALL)) &&
        !(and_with->flags & ANYOF_INVERT))
        cl->flags &= ~ANYOF_UNICODE;
}

/* 'OR' a given class with another one.  Can create false positives */
/* We assume that cl is not inverted */
STATIC void
S_cl_or(const RExC_state_t *pRExC_state, struct regnode_charclass_class *cl, const struct regnode_charclass_class *or_with)
{
    if (or_with->flags & ANYOF_INVERT) {
        /* We do not use
         * (B1 | CL1) | (!B2 & !CL2) = (B1 | !B2 & !CL2) | (CL1 | (!B2 & !CL2))
         *   <= (B1 | !B2) | (CL1 | !CL2)
         * which is wasteful if CL2 is small, but we ignore CL2:
         *   (B1 | CL1) | (!B2 & !CL2) <= (B1 | CL1) | !B2 = (B1 | !B2) | CL1
         * XXXX Can we handle case-fold?  Unclear:
         *   (OK1(i) | OK1(i')) | !(OK1(i) | OK1(i')) =
         *   (OK1(i) | OK1(i')) | (!OK1(i) & !OK1(i'))
         */
        if ( (or_with->flags & ANYOF_LOCALE) == (cl->flags & ANYOF_LOCALE)
             && !(or_with->flags & ANYOF_FOLD)
             && !(cl->flags & ANYOF_FOLD) ) {
            int i;

            for (i = 0; i < ANYOF_BITMAP_SIZE; i++)
                cl->bitmap[i] |= ~or_with->bitmap[i];
        } /* XXXX: logic is complicated otherwise */
        else {
            cl_anything(pRExC_state, cl);
        }
    } else {
        /* (B1 | CL1) | (B2 | CL2) = (B1 | B2) | (CL1 | CL2)) */
        if ( (or_with->flags & ANYOF_LOCALE) == (cl->flags & ANYOF_LOCALE)
             && (!(or_with->flags & ANYOF_FOLD)
                 || (cl->flags & ANYOF_FOLD)) ) {
            int i;

            /* OR char bitmap and class bitmap separately */
            for (i = 0; i < ANYOF_BITMAP_SIZE; i++)
                cl->bitmap[i] |= or_with->bitmap[i];
            if (or_with->flags & ANYOF_CLASS) {
                for (i = 0; i < ANYOF_CLASSBITMAP_SIZE; i++)
                    cl->classflags[i] |= or_with->classflags[i];
                cl->flags |= ANYOF_CLASS;
            }
        }
        else { /* XXXX: logic is complicated, leave it along for a moment. */
            cl_anything(pRExC_state, cl);
        }
    }
    if (or_with->flags & ANYOF_EOS)
        cl->flags |= ANYOF_EOS;

    if (cl->flags & ANYOF_UNICODE && or_with->flags & ANYOF_UNICODE &&
        ARG(cl) != ARG(or_with)) {
        cl->flags |= ANYOF_UNICODE_ALL;
        cl->flags &= ~ANYOF_UNICODE;
    }
    if (or_with->flags & ANYOF_UNICODE_ALL) {
        cl->flags |= ANYOF_UNICODE_ALL;
        cl->flags &= ~ANYOF_UNICODE;
    }
}

/*
 * There are strange code-generation bugs caused on sparc64 by gcc-2.95.2.
 * These need to be revisited when a newer toolchain becomes available.
 */
#if defined(__sparc64__) && defined(__GNUC__)
#   if __GNUC__ < 2 || (__GNUC__ == 2 && __GNUC_MINOR__ < 96)
#       undef  SPARC64_GCC_WORKAROUND
#       define SPARC64_GCC_WORKAROUND 1
#   endif
#endif

/* REx optimizer.  Converts nodes into quickier variants "in place".
   Finds fixed substrings.  */

/* Stops at toplevel WHILEM as well as at "last". At end *scanp is set
   to the position after last scanned or to NULL. */

STATIC I32
S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp, I32 *deltap, regnode *last, scan_data_t *data, U32 flags)
                        /* scanp: Start here (read-write). */
                        /* deltap: Write maxlen-minlen here. */
                        /* last: Stop before this one. */
{
    I32 min = 0, pars = 0, code;
    regnode *scan = *scanp, *next;
    I32 delta = 0;
    int is_inf = (flags & SCF_DO_SUBSTR) && (data->flags & SF_IS_INF);
    int is_inf_internal = 0;            /* The studied chunk is infinite */
    I32 is_par = OP(scan) == OPEN ? ARG(scan) : 0;
    scan_data_t data_fake;
    struct regnode_charclass_class and_with; /* Valid if flags & SCF_DO_STCLASS_OR */

    while (scan && OP(scan) != END && scan < last) {
        /* Peephole optimizer: */

        if (PL_regkind[(U8)OP(scan)] == EXACT) {
            /* Merge several consecutive EXACTish nodes into one. */
            regnode *n = regnext(scan);
            U32 stringok = 1;
#ifdef DEBUGGING
            regnode *stop = scan;
#endif

            next = scan + NODE_SZ_STR(scan);
            /* Skip NOTHING, merge EXACT*. */
            while (n &&
                   ( PL_regkind[(U8)OP(n)] == NOTHING ||
                     (stringok && (OP(n) == OP(scan))))
                   && NEXT_OFF(n)
                   && NEXT_OFF(scan) + NEXT_OFF(n) < I16_MAX) {
                if (OP(n) == TAIL || n > next)
                    stringok = 0;
                if (PL_regkind[(U8)OP(n)] == NOTHING) {
                    NEXT_OFF(scan) += NEXT_OFF(n);
                    next = n + NODE_STEP_REGNODE;
#ifdef DEBUGGING
                    if (stringok)
                        stop = n;
#endif
                    n = regnext(n);
                }
                else if (stringok) {
                    const int oldl = STR_LEN(scan);
                    regnode * const nnext = regnext(n);

                    if (oldl + STR_LEN(n) > U8_MAX)
                        break;
                    NEXT_OFF(scan) += NEXT_OFF(n);
                    STR_LEN(scan) += STR_LEN(n);
                    next = n + NODE_SZ_STR(n);
                    /* Now we can overwrite *n : */
                    Move(STRING(n), STRING(scan) + oldl, STR_LEN(n), char);
#ifdef DEBUGGING
                    stop = next - 1;
#endif
                    n = nnext;
                }
            }

            if (UTF && OP(scan) == EXACTF && STR_LEN(scan) >= 6) {
/*
  Two problematic code points in Unicode casefolding of EXACT nodes:

   U+0390 - GREEK SMALL LETTER IOTA WITH DIALYTIKA AND TONOS
   U+03B0 - GREEK SMALL LETTER UPSILON WITH DIALYTIKA AND TONOS

   which casefold to

   Unicode                      UTF-8

   U+03B9 U+0308 U+0301         0xCE 0xB9 0xCC 0x88 0xCC 0x81
   U+03C5 U+0308 U+0301         0xCF 0x85 0xCC 0x88 0xCC 0x81

   This means that in case-insensitive matching (or "loose matching",
   as Unicode calls it), an EXACTF of length six (the UTF-8 encoded byte
   length of the above casefolded versions) can match a target string
   of length two (the byte length of UTF-8 encoded U+0390 or U+03B0).
   This would rather mess up the minimum length computation.

   What we'll do is to look for the tail four bytes, and then peek
   at the preceding two bytes to see whether we need to decrease
   the minimum length by four (six minus two).

   Thanks to the design of UTF-8, there cannot be false matches:
   A sequence of valid UTF-8 bytes cannot be a subsequence of
   another valid sequence of UTF-8 bytes.

*/
                 char * const s0 = STRING(scan), *s, *t;
                 char * const s1 = s0 + STR_LEN(scan) - 1;
                 char * const s2 = s1 - 4;
                 const char t0[] = "\xcc\x88\xcc\x81";
                 const char * const t1 = t0 + 3;

                 for (s = s0 + 2;
                      s < s2 && (t = ninstr(s, s1, t0, t1));
                      s = t + 4) {
                      if (((U8)t[-1] == 0xB9 && (U8)t[-2] == 0xCE) ||
                          ((U8)t[-1] == 0x85 && (U8)t[-2] == 0xCF))
                           min -= 4;
                 }
            }

#ifdef DEBUGGING
            /* Allow dumping */
            n = scan + NODE_SZ_STR(scan);
            while (n <= stop) {
                if (PL_regkind[(U8)OP(n)] != NOTHING || OP(n) == NOTHING) {
                    OP(n) = OPTIMIZED;
                    NEXT_OFF(n) = 0;
                }
                n++;
            }
#endif
        }
        /* Follow the next-chain of the current node and optimize
           away all the NOTHINGs from it.  */
        if (OP(scan) != CURLYX) {
            const int max = (reg_off_by_arg[OP(scan)]
                       ? I32_MAX
                       /* I32 may be smaller than U16 on CRAYs! */
                       : (I32_MAX < U16_MAX ? I32_MAX : U16_MAX));
            int off = (reg_off_by_arg[OP(scan)] ? ARG(scan) : NEXT_OFF(scan));
            int noff;
            regnode *n = scan;
        
            /* Skip NOTHING and LONGJMP. */
            while ((n = regnext(n))
                   && ((PL_regkind[(U8)OP(n)] == NOTHING && (noff = NEXT_OFF(n)))
                       || ((OP(n) == LONGJMP) && (noff = ARG(n))))
                   && off + noff < max)
                off += noff;
            if (reg_off_by_arg[OP(scan)])
                ARG(scan) = off;
            else
                NEXT_OFF(scan) = off;
        }
        /* The principal pseudo-switch.  Cannot be a switch, since we
           look into several different things.  */
        if (OP(scan) == BRANCH || OP(scan) == BRANCHJ
                   || OP(scan) == IFTHEN || OP(scan) == SUSPEND) {
            next = regnext(scan);
            code = OP(scan);
        
            if (OP(next) == code || code == IFTHEN || code == SUSPEND) {
                I32 max1 = 0, min1 = I32_MAX, num = 0;
                struct regnode_charclass_class accum;
                
                if (flags & SCF_DO_SUBSTR) /* XXXX Add !SUSPEND? */
                    scan_commit(pRExC_state, data); /* Cannot merge strings after this. */
                if (flags & SCF_DO_STCLASS)
                    cl_init_zero(pRExC_state, &accum);
                while (OP(scan) == code) {
                    I32 deltanext, minnext, f = 0, fake;
                    struct regnode_charclass_class this_class;

                    num++;
                    data_fake.flags = 0;
                    if (data) {         
                        data_fake.whilem_c = data->whilem_c;
                        data_fake.last_closep = data->last_closep;
                    }
                    else
                        data_fake.last_closep = &fake;
                    next = regnext(scan);
                    scan = NEXTOPER(scan);
                    if (code != BRANCH)
                        scan = NEXTOPER(scan);
                    if (flags & SCF_DO_STCLASS) {
                        cl_init(pRExC_state, &this_class);
                        data_fake.start_class = &this_class;
                        f = SCF_DO_STCLASS_AND;
                    }           
                    if (flags & SCF_WHILEM_VISITED_POS)
                        f |= SCF_WHILEM_VISITED_POS;
                    /* we suppose the run is continuous, last=next...*/
                    minnext = study_chunk(pRExC_state, &scan, &deltanext,
                                          next, &data_fake, f);
                    if (min1 > minnext)
                        min1 = minnext;
                    if (max1 < minnext + deltanext)
                        max1 = minnext + deltanext;
                    if (deltanext == I32_MAX)
                        is_inf = is_inf_internal = 1;
                    scan = next;
                    if (data_fake.flags & (SF_HAS_PAR|SF_IN_PAR))
                        pars++;
                    if (data && (data_fake.flags & SF_HAS_EVAL))
                        data->flags |= SF_HAS_EVAL;
                    if (data)
                        data->whilem_c = data_fake.whilem_c;
                    if (flags & SCF_DO_STCLASS)
                        cl_or(pRExC_state, &accum, &this_class);
                    if (code == SUSPEND)
                        break;
                }
                if (code == IFTHEN && num < 2) /* Empty ELSE branch */
                    min1 = 0;
                if (flags & SCF_DO_SUBSTR) {
                    data->pos_min += min1;
                    data->pos_delta += max1 - min1;
                    if (max1 != min1 || is_inf)
                        data->longest = &(data->longest_float);
                }
                min += min1;
                delta += max1 - min1;
                if (flags & SCF_DO_STCLASS_OR) {
                    cl_or(pRExC_state, data->start_class, &accum);
                    if (min1) {
                        cl_and(data->start_class, &and_with);
                        flags &= ~SCF_DO_STCLASS;
                    }
                }
                else if (flags & SCF_DO_STCLASS_AND) {
                    if (min1) {
                        cl_and(data->start_class, &accum);
                        flags &= ~SCF_DO_STCLASS;
                    }
                    else {
                        /* Switch to OR mode: cache the old value of
                         * data->start_class */
                        StructCopy(data->start_class, &and_with,
                                   struct regnode_charclass_class);
                        flags &= ~SCF_DO_STCLASS_AND;
                        StructCopy(&accum, data->start_class,
                                   struct regnode_charclass_class);
                        flags |= SCF_DO_STCLASS_OR;
                        data->start_class->flags |= ANYOF_EOS;
                    }
                }

            }
            else if (code == BRANCHJ)   /* single branch is optimized. */
                scan = NEXTOPER(NEXTOPER(scan));
            else                        /* single branch is optimized. */
                scan = NEXTOPER(scan);
            continue;
        }
        else if (OP(scan) == EXACT) {
            I32 l = STR_LEN(scan);
            UV uc;
            if (UTF) {
                const U8 * const s = (U8*)STRING(scan);
                l = utf8_length((U8 *)s, (U8 *)s + l);
                uc = utf8_to_uvchr((U8 *)s, NULL);
            } else {
                uc = *((U8*)STRING(scan));
            }
            min += l;
            if (flags & SCF_DO_SUBSTR) { /* Update longest substr. */
                /* The code below prefers earlier match for fixed
                   offset, later match for variable offset.  */
                if (data->last_end == -1) { /* Update the start info. */
                    data->last_start_min = data->pos_min;
                    data->last_start_max = is_inf
                        ? I32_MAX : data->pos_min + data->pos_delta;
                }
                sv_catpvn(data->last_found, STRING(scan), STR_LEN(scan));
                if (UTF)
                    SvUTF8_on(data->last_found);
                {
                    SV * const sv = data->last_found;
                    MAGIC * const mg = SvUTF8(sv) && SvMAGICAL(sv) ?
                        mg_find(sv, PERL_MAGIC_utf8) : NULL;
                    if (mg && mg->mg_len >= 0)
                        mg->mg_len += utf8_length((U8*)STRING(scan),
                                                  (U8*)STRING(scan)+STR_LEN(scan));
                }
                data->last_end = data->pos_min + l;
                data->pos_min += l; /* As in the first entry. */
                data->flags &= ~SF_BEFORE_EOL;
            }
            if (flags & SCF_DO_STCLASS_AND) {
                /* Check whether it is compatible with what we know already! */
                int compat = 1;

                if (uc >= 0x100 ||
                    (!(data->start_class->flags & (ANYOF_CLASS | ANYOF_LOCALE))
                    && !ANYOF_BITMAP_TEST(data->start_class, uc)
                    && (!(data->start_class->flags & ANYOF_FOLD)
                        || !ANYOF_BITMAP_TEST(data->start_class, PL_fold[uc])))
                    )
                    compat = 0;
                ANYOF_CLASS_ZERO(data->start_class);
                ANYOF_BITMAP_ZERO(data->start_class);
                if (compat)
                    ANYOF_BITMAP_SET(data->start_class, uc);
                data->start_class->flags &= ~ANYOF_EOS;
                if (uc < 0x100)
                  data->start_class->flags &= ~ANYOF_UNICODE_ALL;
            }
            else if (flags & SCF_DO_STCLASS_OR) {
                /* false positive possible if the class is case-folded */
                if (uc < 0x100)
                    ANYOF_BITMAP_SET(data->start_class, uc);
                else
                    data->start_class->flags |= ANYOF_UNICODE_ALL;
                data->start_class->flags &= ~ANYOF_EOS;
                cl_and(data->start_class, &and_with);
            }
            flags &= ~SCF_DO_STCLASS;
        }
        else if (PL_regkind[(U8)OP(scan)] == EXACT) { /* But OP != EXACT! */
            I32 l = STR_LEN(scan);
            UV uc = *((U8*)STRING(scan));

            /* Search for fixed substrings supports EXACT only. */
            if (flags & SCF_DO_SUBSTR) {
                assert(data);
                scan_commit(pRExC_state, data);
            }
            if (UTF) {
                U8 * const s = (U8 *)STRING(scan);
                l = utf8_length(s, s + l);
                uc = utf8_to_uvchr(s, NULL);
            }
            min += l;
            if (flags & SCF_DO_SUBSTR)
                data->pos_min += l;
            if (flags & SCF_DO_STCLASS_AND) {
                /* Check whether it is compatible with what we know already! */
                int compat = 1;

                if (uc >= 0x100 ||
                    (!(data->start_class->flags & (ANYOF_CLASS | ANYOF_LOCALE))
                    && !ANYOF_BITMAP_TEST(data->start_class, uc)
                     && !ANYOF_BITMAP_TEST(data->start_class, PL_fold[uc])))
                    compat = 0;
                ANYOF_CLASS_ZERO(data->start_class);
                ANYOF_BITMAP_ZERO(data->start_class);
                if (compat) {
                    ANYOF_BITMAP_SET(data->start_class, uc);
                    data->start_class->flags &= ~ANYOF_EOS;
                    data->start_class->flags |= ANYOF_FOLD;
                    if (OP(scan) == EXACTFL)
                        data->start_class->flags |= ANYOF_LOCALE;
                }
            }
            else if (flags & SCF_DO_STCLASS_OR) {
                if (data->start_class->flags & ANYOF_FOLD) {
                    /* false positive possible if the class is case-folded.
                       Assume that the locale settings are the same... */
                    if (uc < 0x100)
                        ANYOF_BITMAP_SET(data->start_class, uc);
                    data->start_class->flags &= ~ANYOF_EOS;
                }
                cl_and(data->start_class, &and_with);
            }
            flags &= ~SCF_DO_STCLASS;
        }
        else if (strchr((const char*)PL_varies,OP(scan))) {
            I32 mincount, maxcount, minnext, deltanext, fl = 0;
            I32 f = flags, pos_before = 0;
            regnode * const oscan = scan;
            struct regnode_charclass_class this_class;
            struct regnode_charclass_class *oclass = NULL;
            I32 next_is_eval = 0;

            switch (PL_regkind[(U8)OP(scan)]) {
            case WHILEM:                /* End of (?:...)* . */
                scan = NEXTOPER(scan);
                goto finish;
            case PLUS:
                if (flags & (SCF_DO_SUBSTR | SCF_DO_STCLASS)) {
                    next = NEXTOPER(scan);
                    if (OP(next) == EXACT || (flags & SCF_DO_STCLASS)) {
                        mincount = 1;
                        maxcount = REG_INFTY;
                        next = regnext(scan);
                        scan = NEXTOPER(scan);
                        goto do_curly;
                    }
                }
                if (flags & SCF_DO_SUBSTR)
                    data->pos_min++;
                min++;
                /* Fall through. */
            case STAR:
                if (flags & SCF_DO_STCLASS) {
                    mincount = 0;
                    maxcount = REG_INFTY;
                    next = regnext(scan);
                    scan = NEXTOPER(scan);
                    goto do_curly;
                }
                is_inf = is_inf_internal = 1;
                scan = regnext(scan);
                if (flags & SCF_DO_SUBSTR) {
                    scan_commit(pRExC_state, data); /* Cannot extend fixed substrings */
                    data->longest = &(data->longest_float);
                }
                goto optimize_curly_tail;
            case CURLY:
                mincount = ARG1(scan);
                maxcount = ARG2(scan);
                next = regnext(scan);
                if (OP(scan) == CURLYX) {
                    I32 lp = (data ? *(data->last_closep) : 0);

                    scan->flags = ((lp <= U8_MAX) ? lp : U8_MAX);
                }
                scan = NEXTOPER(scan) + EXTRA_STEP_2ARGS;
                next_is_eval = (OP(scan) == EVAL);
              do_curly:
                if (flags & SCF_DO_SUBSTR) {
                    if (mincount == 0) scan_commit(pRExC_state,data); /* Cannot extend fixed substrings */
                    pos_before = data->pos_min;
                }
                if (data) {
                    fl = data->flags;
                    data->flags &= ~(SF_HAS_PAR|SF_IN_PAR|SF_HAS_EVAL);
                    if (is_inf)
                        data->flags |= SF_IS_INF;
                }
                if (flags & SCF_DO_STCLASS) {
                    cl_init(pRExC_state, &this_class);
                    oclass = data->start_class;
                    data->start_class = &this_class;
                    f |= SCF_DO_STCLASS_AND;
                    f &= ~SCF_DO_STCLASS_OR;
                }
                /* These are the cases when once a subexpression
                   fails at a particular position, it cannot succeed
                   even after backtracking at the enclosing scope.
                
                   XXXX what if minimal match and we are at the
                        initial run of {n,m}? */
                if ((mincount != maxcount - 1) && (maxcount != REG_INFTY))
                    f &= ~SCF_WHILEM_VISITED_POS;

                /* This will finish on WHILEM, setting scan, or on NULL: */
                minnext = study_chunk(pRExC_state, &scan, &deltanext, last, data,
                                      mincount == 0
                                        ? (f & ~SCF_DO_SUBSTR) : f);

                if (flags & SCF_DO_STCLASS)
                    data->start_class = oclass;
                if (mincount == 0 || minnext == 0) {
                    if (flags & SCF_DO_STCLASS_OR) {
                        cl_or(pRExC_state, data->start_class, &this_class);
                    }
                    else if (flags & SCF_DO_STCLASS_AND) {
                        /* Switch to OR mode: cache the old value of
                         * data->start_class */
                        StructCopy(data->start_class, &and_with,
                                   struct regnode_charclass_class);
                        flags &= ~SCF_DO_STCLASS_AND;
                        StructCopy(&this_class, data->start_class,
                                   struct regnode_charclass_class);
                        flags |= SCF_DO_STCLASS_OR;
                        data->start_class->flags |= ANYOF_EOS;
                    }
                } else {                /* Non-zero len */
                    if (flags & SCF_DO_STCLASS_OR) {
                        cl_or(pRExC_state, data->start_class, &this_class);
                        cl_and(data->start_class, &and_with);
                    }
                    else if (flags & SCF_DO_STCLASS_AND)
                        cl_and(data->start_class, &this_class);
                    flags &= ~SCF_DO_STCLASS;
                }
                if (!scan)              /* It was not CURLYX, but CURLY. */
                    scan = next;
                if ( /* ? quantifier ok, except for (?{ ... }) */
                    (next_is_eval || !(mincount == 0 && maxcount == 1))
                    && (minnext == 0) && (deltanext == 0)
                    && data && !(data->flags & (SF_HAS_PAR|SF_IN_PAR))
                    && maxcount <= REG_INFTY/3 /* Complement check for big count */
                    && ckWARN(WARN_REGEXP))
                {
                    vWARN(RExC_parse,
                          "Quantifier unexpected on zero-length expression");
                }

                min += minnext * mincount;
                is_inf_internal |= ((maxcount == REG_INFTY
                                     && (minnext + deltanext) > 0)
                                    || deltanext == I32_MAX);
                is_inf |= is_inf_internal;
                delta += (minnext + deltanext) * maxcount - minnext * mincount;

                /* Try powerful optimization CURLYX => CURLYN. */
                if (  OP(oscan) == CURLYX && data
                      && data->flags & SF_IN_PAR
                      && !(data->flags & SF_HAS_EVAL)
                      && !deltanext && minnext == 1 ) {
                    /* Try to optimize to CURLYN.  */
                    regnode *nxt = NEXTOPER(oscan) + EXTRA_STEP_2ARGS;
                    regnode * const nxt1 = nxt;
#ifdef DEBUGGING
                    regnode *nxt2;
#endif

                    /* Skip open. */
                    nxt = regnext(nxt);
                    if (!strchr((const char*)PL_simple,OP(nxt))
                        && !(PL_regkind[(U8)OP(nxt)] == EXACT
                             && STR_LEN(nxt) == 1))
                        goto nogo;
#ifdef DEBUGGING
                    nxt2 = nxt;
#endif
                    nxt = regnext(nxt);
                    if (OP(nxt) != CLOSE)
                        goto nogo;
                    /* Now we know that nxt2 is the only contents: */
                    oscan->flags = (U8)ARG(nxt);
                    OP(oscan) = CURLYN;
                    OP(nxt1) = NOTHING; /* was OPEN. */
#ifdef DEBUGGING
                    OP(nxt1 + 1) = OPTIMIZED; /* was count. */
                    NEXT_OFF(nxt1+ 1) = 0; /* just for consistancy. */
                    NEXT_OFF(nxt2) = 0; /* just for consistancy with CURLY. */
                    OP(nxt) = OPTIMIZED;        /* was CLOSE. */
                    OP(nxt + 1) = OPTIMIZED; /* was count. */
                    NEXT_OFF(nxt+ 1) = 0; /* just for consistancy. */
#endif
                }
              nogo:

                /* Try optimization CURLYX => CURLYM. */
                if (  OP(oscan) == CURLYX && data
                      && !(data->flags & SF_HAS_PAR)
                      && !(data->flags & SF_HAS_EVAL)
                      && !deltanext     /* atom is fixed width */
                      && minnext != 0   /* CURLYM can't handle zero width */
                ) {
                    /* XXXX How to optimize if data == 0? */
                    /* Optimize to a simpler form.  */
                    regnode *nxt = NEXTOPER(oscan) + EXTRA_STEP_2ARGS; /* OPEN */
                    regnode *nxt2;

                    OP(oscan) = CURLYM;
                    while ( (nxt2 = regnext(nxt)) /* skip over embedded stuff*/
                            && (OP(nxt2) != WHILEM))
                        nxt = nxt2;
                    OP(nxt2)  = SUCCEED; /* Whas WHILEM */
                    /* Need to optimize away parenths. */
                    if (data->flags & SF_IN_PAR) {
                        /* Set the parenth number.  */
                        regnode *nxt1 = NEXTOPER(oscan) + EXTRA_STEP_2ARGS; /* OPEN*/

                        if (OP(nxt) != CLOSE)
                            FAIL("Panic opt close");
                        oscan->flags = (U8)ARG(nxt);
                        OP(nxt1) = OPTIMIZED;   /* was OPEN. */
                        OP(nxt) = OPTIMIZED;    /* was CLOSE. */
#ifdef DEBUGGING
                        OP(nxt1 + 1) = OPTIMIZED; /* was count. */
                        OP(nxt + 1) = OPTIMIZED; /* was count. */
                        NEXT_OFF(nxt1 + 1) = 0; /* just for consistancy. */
                        NEXT_OFF(nxt + 1) = 0; /* just for consistancy. */
#endif
#if 0
                        while ( nxt1 && (OP(nxt1) != WHILEM)) {
                            regnode *nnxt = regnext(nxt1);
                        
                            if (nnxt == nxt) {
                                if (reg_off_by_arg[OP(nxt1)])
                                    ARG_SET(nxt1, nxt2 - nxt1);
                                else if (nxt2 - nxt1 < U16_MAX)
                                    NEXT_OFF(nxt1) = nxt2 - nxt1;
                                else
                                    OP(nxt) = NOTHING;  /* Cannot beautify */
                            }
                            nxt1 = nnxt;
                        }
#endif
                        /* Optimize again: */
                        study_chunk(pRExC_state, &nxt1, &deltanext, nxt,
                                    NULL, 0);
                    }
                    else
                        oscan->flags = 0;
                }
                else if ((OP(oscan) == CURLYX)
                         && (flags & SCF_WHILEM_VISITED_POS)
                         /* See the comment on a similar expression above.
                            However, this time it not a subexpression
                            we care about, but the expression itself. */
                         && (maxcount == REG_INFTY)
                         && data && ++data->whilem_c < 16) {
                    /* This stays as CURLYX, we can put the count/of pair. */
                    /* Find WHILEM (as in regexec.c) */
                    regnode *nxt = oscan + NEXT_OFF(oscan);

                    if (OP(PREVOPER(nxt)) == NOTHING) /* LONGJMP */
                        nxt += ARG(nxt);
                    PREVOPER(nxt)->flags = (U8)(data->whilem_c
                        | (RExC_whilem_seen << 4)); /* On WHILEM */
                }
                if (data && fl & (SF_HAS_PAR|SF_IN_PAR))
                    pars++;
                if (flags & SCF_DO_SUBSTR) {
                    SV *last_str = NULL;
                    int counted = mincount != 0;

                    if (data->last_end > 0 && mincount != 0) { /* Ends with a string. */
#if defined(SPARC64_GCC_WORKAROUND)
                        I32 b = 0;
                        STRLEN l = 0;
                        const char *s = NULL;
                        I32 old = 0;

                        if (pos_before >= data->last_start_min)
                            b = pos_before;
                        else
                            b = data->last_start_min;

                        l = 0;
                        s = SvPV_const(data->last_found, l);
                        old = b - data->last_start_min;

#else
                        I32 b = pos_before >= data->last_start_min
                            ? pos_before : data->last_start_min;
                        STRLEN l;
                        const char * const s = SvPV_const(data->last_found, l);
                        I32 old = b - data->last_start_min;
#endif

                        if (UTF)
                            old = utf8_hop((U8*)s, old) - (U8*)s;
                        
                        l -= old;
                        /* Get the added string: */
                        last_str = newSVpvn(s  + old, l);
                        if (UTF)
                            SvUTF8_on(last_str);
                        if (deltanext == 0 && pos_before == b) {
                            /* What was added is a constant string */
                            if (mincount > 1) {
                                SvGROW(last_str, (mincount * l) + 1);
                                repeatcpy(SvPVX(last_str) + l,
                                          SvPVX_const(last_str), l, mincount - 1);
                                SvCUR_set(last_str, SvCUR(last_str) * mincount);
                                /* Add additional parts. */
                                SvCUR_set(data->last_found,
                                          SvCUR(data->last_found) - l);
                                sv_catsv(data->last_found, last_str);
                                {
                                    SV * sv = data->last_found;
                                    MAGIC *mg =
                                        SvUTF8(sv) && SvMAGICAL(sv) ?
                                        mg_find(sv, PERL_MAGIC_utf8) : NULL;
                                    if (mg && mg->mg_len >= 0)
                                        mg->mg_len += CHR_SVLEN(last_str);
                                }
                                data->last_end += l * (mincount - 1);
                            }
                        } else {
                            /* start offset must point into the last copy */
                            data->last_start_min += minnext * (mincount - 1);
                            data->last_start_max += is_inf ? I32_MAX
                                : (maxcount - 1) * (minnext + data->pos_delta);
                        }
                    }
                    /* It is counted once already... */
                    data->pos_min += minnext * (mincount - counted);
                    data->pos_delta += - counted * deltanext +
                        (minnext + deltanext) * maxcount - minnext * mincount;
                    if (mincount != maxcount) {
                         /* Cannot extend fixed substrings found inside
                            the group.  */
                        scan_commit(pRExC_state,data);
                        if (mincount && last_str) {
                            SV * const sv = data->last_found;
                            MAGIC * const mg = SvUTF8(sv) && SvMAGICAL(sv) ?
                                mg_find(sv, PERL_MAGIC_utf8) : NULL;

                            if (mg)
                                mg->mg_len = -1;
                            sv_setsv(sv, last_str);
                            data->last_end = data->pos_min;
                            data->last_start_min =
                                data->pos_min - CHR_SVLEN(last_str);
                            data->last_start_max = is_inf
                                ? I32_MAX
                                : data->pos_min + data->pos_delta
                                - CHR_SVLEN(last_str);
                        }
                        data->longest = &(data->longest_float);
                    }
                    SvREFCNT_dec(last_str);
                }
                if (data && (fl & SF_HAS_EVAL))
                    data->flags |= SF_HAS_EVAL;
              optimize_curly_tail:
                if (OP(oscan) != CURLYX) {
                    while (PL_regkind[(U8)OP(next = regnext(oscan))] == NOTHING
                           && NEXT_OFF(next))
                        NEXT_OFF(oscan) += NEXT_OFF(next);
                }
                continue;
            default:                    /* REF and CLUMP only? */
                if (flags & SCF_DO_SUBSTR) {
                    scan_commit(pRExC_state,data);      /* Cannot expect anything... */
                    data->longest = &(data->longest_float);
                }
                is_inf = is_inf_internal = 1;
                if (flags & SCF_DO_STCLASS_OR)
                    cl_anything(pRExC_state, data->start_class);
                flags &= ~SCF_DO_STCLASS;
                break;
            }
        }
        else if (strchr((const char*)PL_simple,OP(scan))) {
            int value = 0;

            if (flags & SCF_DO_SUBSTR) {
                scan_commit(pRExC_state,data);
                data->pos_min++;
            }
            min++;
            if (flags & SCF_DO_STCLASS) {
                data->start_class->flags &= ~ANYOF_EOS; /* No match on empty */

                /* Some of the logic below assumes that switching
                   locale on will only add false positives. */
                switch (PL_regkind[(U8)OP(scan)]) {
                case SANY:
                default:
                  do_default:
                    /* Perl_croak(aTHX_ "panic: unexpected simple REx opcode %d", OP(scan)); */
                    if (flags & SCF_DO_STCLASS_OR) /* Allow everything */
                        cl_anything(pRExC_state, data->start_class);
                    break;
                case REG_ANY:
                    if (OP(scan) == SANY)
                        goto do_default;
                    if (flags & SCF_DO_STCLASS_OR) { /* Everything but \n */
                        value = (ANYOF_BITMAP_TEST(data->start_class,'\n')
                                 || (data->start_class->flags & ANYOF_CLASS));
                        cl_anything(pRExC_state, data->start_class);
                    }
                    if (flags & SCF_DO_STCLASS_AND || !value)
                        ANYOF_BITMAP_CLEAR(data->start_class,'\n');
                    break;
                case ANYOF:
                    if (flags & SCF_DO_STCLASS_AND)
                        cl_and(data->start_class,
                               (struct regnode_charclass_class*)scan);
                    else
                        cl_or(pRExC_state, data->start_class,
                              (struct regnode_charclass_class*)scan);
                    break;
                case ALNUM:
                    if (flags & SCF_DO_STCLASS_AND) {
                        if (!(data->start_class->flags & ANYOF_LOCALE)) {
                            ANYOF_CLASS_CLEAR(data->start_class,ANYOF_NALNUM);
                            for (value = 0; value < 256; value++)
                                if (!isALNUM(value))
                                    ANYOF_BITMAP_CLEAR(data->start_class, value);
                        }
                    }
                    else {
                        if (data->start_class->flags & ANYOF_LOCALE)
                            ANYOF_CLASS_SET(data->start_class,ANYOF_ALNUM);
                        else {
                            for (value = 0; value < 256; value++)
                                if (isALNUM(value))
                                    ANYOF_BITMAP_SET(data->start_class, value);                 
                        }
                    }
                    break;
                case ALNUML:
                    if (flags & SCF_DO_STCLASS_AND) {
                        if (data->start_class->flags & ANYOF_LOCALE)
                            ANYOF_CLASS_CLEAR(data->start_class,ANYOF_NALNUM);
                    }
                    else {
                        ANYOF_CLASS_SET(data->start_class,ANYOF_ALNUM);
                        data->start_class->flags |= ANYOF_LOCALE;
                    }
                    break;
                case NALNUM:
                    if (flags & SCF_DO_STCLASS_AND) {
                        if (!(data->start_class->flags & ANYOF_LOCALE)) {
                            ANYOF_CLASS_CLEAR(data->start_class,ANYOF_ALNUM);
                            for (value = 0; value < 256; value++)
                                if (isALNUM(value))
                                    ANYOF_BITMAP_CLEAR(data->start_class, value);
                        }
                    }
                    else {
                        if (data->start_class->flags & ANYOF_LOCALE)
                            ANYOF_CLASS_SET(data->start_class,ANYOF_NALNUM);
                        else {
                            for (value = 0; value < 256; value++)
                                if (!isALNUM(value))
                                    ANYOF_BITMAP_SET(data->start_class, value);                 
                        }
                    }
                    break;
                case NALNUML:
                    if (flags & SCF_DO_STCLASS_AND) {
                        if (data->start_class->flags & ANYOF_LOCALE)
                            ANYOF_CLASS_CLEAR(data->start_class,ANYOF_ALNUM);
                    }
                    else {
                        data->start_class->flags |= ANYOF_LOCALE;
                        ANYOF_CLASS_SET(data->start_class,ANYOF_NALNUM);
                    }
                    break;
                case SPACE:
                    if (flags & SCF_DO_STCLASS_AND) {
                        if (!(data->start_class->flags & ANYOF_LOCALE)) {
                            ANYOF_CLASS_CLEAR(data->start_class,ANYOF_NSPACE);
                            for (value = 0; value < 256; value++)
                                if (!isSPACE(value))
                                    ANYOF_BITMAP_CLEAR(data->start_class, value);
                        }
                    }
                    else {
                        if (data->start_class->flags & ANYOF_LOCALE)
                            ANYOF_CLASS_SET(data->start_class,ANYOF_SPACE);
                        else {
                            for (value = 0; value < 256; value++)
                                if (isSPACE(value))
                                    ANYOF_BITMAP_SET(data->start_class, value);                 
                        }
                    }
                    break;
                case SPACEL:
                    if (flags & SCF_DO_STCLASS_AND) {
                        if (data->start_class->flags & ANYOF_LOCALE)
                            ANYOF_CLASS_CLEAR(data->start_class,ANYOF_NSPACE);
                    }
                    else {
                        data->start_class->flags |= ANYOF_LOCALE;
                        ANYOF_CLASS_SET(data->start_class,ANYOF_SPACE);
                    }
                    break;
                case NSPACE:
                    if (flags & SCF_DO_STCLASS_AND) {
                        if (!(data->start_class->flags & ANYOF_LOCALE)) {
                            ANYOF_CLASS_CLEAR(data->start_class,ANYOF_SPACE);
                            for (value = 0; value < 256; value++)
                                if (isSPACE(value))
                                    ANYOF_BITMAP_CLEAR(data->start_class, value);
                        }
                    }
                    else {
                        if (data->start_class->flags & ANYOF_LOCALE)
                            ANYOF_CLASS_SET(data->start_class,ANYOF_NSPACE);
                        else {
                            for (value = 0; value < 256; value++)
                                if (!isSPACE(value))
                                    ANYOF_BITMAP_SET(data->start_class, value);                 
                        }
                    }
                    break;
                case NSPACEL:
                    if (flags & SCF_DO_STCLASS_AND) {
                        if (data->start_class->flags & ANYOF_LOCALE) {
                            ANYOF_CLASS_CLEAR(data->start_class,ANYOF_SPACE);
                            for (value = 0; value < 256; value++)
                                if (!isSPACE(value))
                                    ANYOF_BITMAP_CLEAR(data->start_class, value);
                        }
                    }
                    else {
                        data->start_class->flags |= ANYOF_LOCALE;
                        ANYOF_CLASS_SET(data->start_class,ANYOF_NSPACE);
                    }
                    break;
                case DIGIT:
                    if (flags & SCF_DO_STCLASS_AND) {
                        ANYOF_CLASS_CLEAR(data->start_class,ANYOF_NDIGIT);
                        for (value = 0; value < 256; value++)
                            if (!isDIGIT(value))
                                ANYOF_BITMAP_CLEAR(data->start_class, value);
                    }
                    else {
                        if (data->start_class->flags & ANYOF_LOCALE)
                            ANYOF_CLASS_SET(data->start_class,ANYOF_DIGIT);
                        else {
                            for (value = 0; value < 256; value++)
                                if (isDIGIT(value))
                                    ANYOF_BITMAP_SET(data->start_class, value);                 
                        }
                    }
                    break;
                case NDIGIT:
                    if (flags & SCF_DO_STCLASS_AND) {
                        ANYOF_CLASS_CLEAR(data->start_class,ANYOF_DIGIT);
                        for (value = 0; value < 256; value++)
                            if (isDIGIT(value))
                                ANYOF_BITMAP_CLEAR(data->start_class, value);
                    }
                    else {
                        if (data->start_class->flags & ANYOF_LOCALE)
                            ANYOF_CLASS_SET(data->start_class,ANYOF_NDIGIT);
                        else {
                            for (value = 0; value < 256; value++)
                                if (!isDIGIT(value))
                                    ANYOF_BITMAP_SET(data->start_class, value);                 
                        }
                    }
                    break;
                }
                if (flags & SCF_DO_STCLASS_OR)
                    cl_and(data->start_class, &and_with);
                flags &= ~SCF_DO_STCLASS;
            }
        }
        else if (PL_regkind[(U8)OP(scan)] == EOL && flags & SCF_DO_SUBSTR) {
            data->flags |= (OP(scan) == MEOL
                            ? SF_BEFORE_MEOL
                            : SF_BEFORE_SEOL);
        }
        else if (  PL_regkind[(U8)OP(scan)] == BRANCHJ
                 /* Lookbehind, or need to calculate parens/evals/stclass: */
                   && (scan->flags || data || (flags & SCF_DO_STCLASS))
                   && (OP(scan) == IFMATCH || OP(scan) == UNLESSM)) {
            /* Lookahead/lookbehind */
            I32 deltanext, minnext, fake = 0;
            regnode *nscan;
            struct regnode_charclass_class intrnl;
            int f = 0;

            data_fake.flags = 0;
            if (data) {         
                data_fake.whilem_c = data->whilem_c;
                data_fake.last_closep = data->last_closep;
            }
            else
                data_fake.last_closep = &fake;
            if ( flags & SCF_DO_STCLASS && !scan->flags
                 && OP(scan) == IFMATCH ) { /* Lookahead */
                cl_init(pRExC_state, &intrnl);
                data_fake.start_class = &intrnl;
                f |= SCF_DO_STCLASS_AND;
            }
            if (flags & SCF_WHILEM_VISITED_POS)
                f |= SCF_WHILEM_VISITED_POS;
            next = regnext(scan);
            nscan = NEXTOPER(NEXTOPER(scan));
            minnext = study_chunk(pRExC_state, &nscan, &deltanext, last, &data_fake, f);
            if (scan->flags) {
                if (deltanext) {
                    vFAIL("Variable length lookbehind not implemented");
                }
                else if (minnext > U8_MAX) {
                    vFAIL2("Lookbehind longer than %"UVuf" not implemented", (UV)U8_MAX);
                }
                scan->flags = (U8)minnext;
            }
            if (data && data_fake.flags & (SF_HAS_PAR|SF_IN_PAR))
                pars++;
            if (data && (data_fake.flags & SF_HAS_EVAL))
                data->flags |= SF_HAS_EVAL;
            if (data)
                data->whilem_c = data_fake.whilem_c;
            if (f & SCF_DO_STCLASS_AND) {
                const int was = (data->start_class->flags & ANYOF_EOS);

                cl_and(data->start_class, &intrnl);
                if (was)
                    data->start_class->flags |= ANYOF_EOS;
            }
        }
        else if (OP(scan) == OPEN) {
            pars++;
        }
        else if (OP(scan) == CLOSE) {
            if ((I32)ARG(scan) == is_par) {
                next = regnext(scan);

                if ( next && (OP(next) != WHILEM) && next < last)
                    is_par = 0;         /* Disable optimization */
            }
            if (data)
                *(data->last_closep) = ARG(scan);
        }
        else if (OP(scan) == EVAL) {
                if (data)
                    data->flags |= SF_HAS_EVAL;
        }
        else if (OP(scan) == LOGICAL && scan->flags == 2) { /* Embedded follows */
                if (flags & SCF_DO_SUBSTR) {
                    scan_commit(pRExC_state,data);
                    data->longest = &(data->longest_float);
                }
                is_inf = is_inf_internal = 1;
                if (flags & SCF_DO_STCLASS_OR) /* Allow everything */
                    cl_anything(pRExC_state, data->start_class);
                flags &= ~SCF_DO_STCLASS;
        }
        /* Else: zero-length, ignore. */
        scan = regnext(scan);
    }

  finish:
    *scanp = scan;
    *deltap = is_inf_internal ? I32_MAX : delta;
    if (flags & SCF_DO_SUBSTR && is_inf)
        data->pos_delta = I32_MAX - data->pos_min;
    if (is_par > U8_MAX)
        is_par = 0;
    if (is_par && pars==1 && data) {
        data->flags |= SF_IN_PAR;
        data->flags &= ~SF_HAS_PAR;
    }
    else if (pars && data) {
        data->flags |= SF_HAS_PAR;
        data->flags &= ~SF_IN_PAR;
    }
    if (flags & SCF_DO_STCLASS_OR)
        cl_and(data->start_class, &and_with);
    return min;
}

STATIC U32
S_add_data(RExC_state_t *pRExC_state, U32 n, const char *s)
{
    U32 count = RExC_rx->data ? RExC_rx->data->count : 0;

    Renewc(RExC_rx->data,
           sizeof(*RExC_rx->data) + sizeof(void*) * (count + n - 1),
           char, struct reg_data);
    if(count)
        Renew(RExC_rx->data->what, count + n, U8);
    else
        Newx(RExC_rx->data->what, n, U8);
    RExC_rx->data->count = count + n;
    Copy(s, RExC_rx->data->what + count, n, U8);
    return count;
}

void
Perl_reginitcolors(pTHX)
{
    const char * const s = PerlEnv_getenv("PERL_RE_COLORS");
    if (s) {
        char *t = savepv(s);
        int i = 0;
        PL_colors[0] = t;
        while (++i < 6) {
            t = strchr(t, '\t');
            if (t) {
                *t = '\0';
                PL_colors[i] = ++t;
            }
            else
                PL_colors[i] = t = (char *)"";
        }
    } else {
        int i = 0;
        while (i < 6)
            PL_colors[i++] = (char *)"";
    }
    PL_colorset = 1;
}


/*
 - pregcomp - compile a regular expression into internal code
 *
 * We can't allocate space until we know how big the compiled form will be,
 * but we can't compile it (and thus know how big it is) until we've got a
 * place to put the code.  So we cheat:  we compile it twice, once with code
 * generation turned off and size counting turned on, and once "for real".
 * This also means that we don't allocate space until we are sure that the
 * thing really will compile successfully, and we never have to move the
 * code and thus invalidate pointers into it.  (Note that it has to be in
 * one piece because free() must be able to free it all.) [NB: not true in perl]
 *
 * Beware that the optimization-preparation code in here knows about some
 * of the structure of the compiled regexp.  [I'll say.]
 */
regexp *
Perl_pregcomp(pTHX_ char *exp, char *xend, PMOP *pm)
{
    register regexp *r;
    regnode *scan;
    regnode *first;
    I32 flags;
    I32 minlen = 0;
    I32 sawplus = 0;
    I32 sawopen = 0;
    scan_data_t data;
    RExC_state_t RExC_state;
    RExC_state_t *pRExC_state = &RExC_state;

    if (exp == NULL)
        FAIL("NULL regexp argument");

    RExC_utf8 = pm->op_pmdynflags & PMdf_CMP_UTF8;

    RExC_precomp = exp;
    DEBUG_r({
         if (!PL_colorset) reginitcolors();
         PerlIO_printf(Perl_debug_log, "%sCompiling REx%s `%s%*s%s'\n",
                       PL_colors[4],PL_colors[5],PL_colors[0],
                       (int)(xend - exp), RExC_precomp, PL_colors[1]);
    });
    RExC_flags = pm->op_pmflags;
    RExC_sawback = 0;

    RExC_seen = 0;
    RExC_seen_zerolen = *exp == '^' ? -1 : 0;
    RExC_seen_evals = 0;
    RExC_extralen = 0;

    /* First pass: determine size, legality. */
    RExC_parse = exp;
    RExC_start = exp;
    RExC_end = xend;
    RExC_naughty = 0;
    RExC_npar = 1;
    RExC_size = 0L;
    RExC_emit = &PL_regdummy;
    RExC_whilem_seen = 0;
#if 0 /* REGC() is (currently) a NOP at the first pass.
       * Clever compilers notice this and complain. --jhi */
    REGC((U8)REG_MAGIC, (char*)RExC_emit);
#endif
    if (reg(pRExC_state, 0, &flags) == NULL) {
        RExC_precomp = NULL;
        return(NULL);
    }
    DEBUG_r(PerlIO_printf(Perl_debug_log, "size %"IVdf" ", (IV)RExC_size));

    /* Small enough for pointer-storage convention?
       If extralen==0, this means that we will not need long jumps. */
    if (RExC_size >= 0x10000L && RExC_extralen)
        RExC_size += RExC_extralen;
    else
        RExC_extralen = 0;
    if (RExC_whilem_seen > 15)
        RExC_whilem_seen = 15;

    /* Allocate space and initialize. */
    Newxc(r, sizeof(regexp) + (unsigned)RExC_size * sizeof(regnode),
         char, regexp);
    if (r == NULL)
        FAIL("Regexp out of space");

#ifdef DEBUGGING
    /* avoid reading uninitialized memory in DEBUGGING code in study_chunk() */
    Zero(r, sizeof(regexp) + (unsigned)RExC_size * sizeof(regnode), char);
#endif
    r->refcnt = 1;
    r->prelen = xend - exp;
    r->precomp = savepvn(RExC_precomp, r->prelen);
    r->subbeg = NULL;
    r->reganch = pm->op_pmflags & PMf_COMPILETIME;
    r->nparens = RExC_npar - 1; /* set early to validate backrefs */
    r->lastparen = 0;                   /* mg.c reads this.  */

    r->substrs = 0;                     /* Useful during FAIL. */
    r->startp = 0;                      /* Useful during FAIL. */
    r->endp = 0;                        /* Useful during FAIL. */

    Newxz(r->offsets, 2*RExC_size+1, U32); /* MJD 20001228 */
    if (r->offsets) {
        r->offsets[0] = RExC_size;
    }
    DEBUG_r(PerlIO_printf(Perl_debug_log, 
                          "%s %"UVuf" bytes for offset annotations.\n",
                          r->offsets ? "Got" : "Couldn't get",
                          (UV)((2*RExC_size+1) * sizeof(U32))));

    RExC_rx = r;

    /* Second pass: emit code. */
    RExC_flags = pm->op_pmflags;        /* don't let top level (?i) bleed */
    RExC_parse = exp;
    RExC_end = xend;
    RExC_naughty = 0;
    RExC_npar = 1;
    RExC_emit_start = r->program;
    RExC_emit = r->program;
    /* Store the count of eval-groups for security checks: */
    RExC_emit->next_off = (U16)((RExC_seen_evals > U16_MAX) ? U16_MAX : RExC_seen_evals);
    REGC((U8)REG_MAGIC, (char*) RExC_emit++);
    r->data = 0;
    if (reg(pRExC_state, 0, &flags) == NULL)
        return(NULL);

    /* Dig out information for optimizations. */
    r->reganch = pm->op_pmflags & PMf_COMPILETIME; /* Again? */
    pm->op_pmflags = RExC_flags;
    if (UTF)
        r->reganch |= ROPT_UTF8;        /* Unicode in it? */
    r->regstclass = NULL;
    if (RExC_naughty >= 10)     /* Probably an expensive pattern. */
        r->reganch |= ROPT_NAUGHTY;
    scan = r->program + 1;              /* First BRANCH. */

    /* XXXX To minimize changes to RE engine we always allocate
       3-units-long substrs field. */
    Newxz(r->substrs, 1, struct reg_substr_data);

    StructCopy(&zero_scan_data, &data, scan_data_t);
    /* XXXX Should not we check for something else?  Usually it is OPEN1... */
    if (OP(scan) != BRANCH) {   /* Only one top-level choice. */
        I32 fake;
        STRLEN longest_float_length, longest_fixed_length;
        struct regnode_charclass_class ch_class;
        int stclass_flag;
        I32 last_close = 0;

        first = scan;
        /* Skip introductions and multiplicators >= 1. */
        while ((OP(first) == OPEN && (sawopen = 1)) ||
               /* An OR of *one* alternative - should not happen now. */
            (OP(first) == BRANCH && OP(regnext(first)) != BRANCH) ||
            (OP(first) == PLUS) ||
            (OP(first) == MINMOD) ||
               /* An {n,m} with n>0 */
            (PL_regkind[(U8)OP(first)] == CURLY && ARG1(first) > 0) ) {
                if (OP(first) == PLUS)
                    sawplus = 1;
                else
                    first += regarglen[(U8)OP(first)];
                first = NEXTOPER(first);
        }

        /* Starting-point info. */
      again:
        if (PL_regkind[(U8)OP(first)] == EXACT) {
            if (OP(first) == EXACT)
                NOOP;   /* Empty, get anchored substr later. */
            else if ((OP(first) == EXACTF || OP(first) == EXACTFL))
                r->regstclass = first;
        }
        else if (strchr((const char*)PL_simple,OP(first)))
            r->regstclass = first;
        else if (PL_regkind[(U8)OP(first)] == BOUND ||
                 PL_regkind[(U8)OP(first)] == NBOUND)
            r->regstclass = first;
        else if (PL_regkind[(U8)OP(first)] == BOL) {
            r->reganch |= (OP(first) == MBOL
                           ? ROPT_ANCH_MBOL
                           : (OP(first) == SBOL
                              ? ROPT_ANCH_SBOL
                              : ROPT_ANCH_BOL));
            first = NEXTOPER(first);
            goto again;
        }
        else if (OP(first) == GPOS) {
            r->reganch |= ROPT_ANCH_GPOS;
            first = NEXTOPER(first);
            goto again;
        }
        else if ((!sawopen || !RExC_sawback) &&
            (OP(first) == STAR &&
            PL_regkind[(U8)OP(NEXTOPER(first))] == REG_ANY) &&
            !(r->reganch & ROPT_ANCH) )
        {
            /* turn .* into ^.* with an implied $*=1 */
            const int type =
                (OP(NEXTOPER(first)) == REG_ANY)
                    ? ROPT_ANCH_MBOL
                    : ROPT_ANCH_SBOL;
            r->reganch |= type | ROPT_IMPLICIT;
            first = NEXTOPER(first);
            goto again;
        }
        if (sawplus && (!sawopen || !RExC_sawback)
            && !(RExC_seen & REG_SEEN_EVAL)) /* May examine pos and $& */
            /* x+ must match at the 1st pos of run of x's */
            r->reganch |= ROPT_SKIP;

        /* Scan is after the zeroth branch, first is atomic matcher. */
        DEBUG_r(PerlIO_printf(Perl_debug_log, "first at %"IVdf"\n",
                              (IV)(first - scan + 1)));
        /*
        * If there's something expensive in the r.e., find the
        * longest literal string that must appear and make it the
        * regmust.  Resolve ties in favor of later strings, since
        * the regstart check works with the beginning of the r.e.
        * and avoiding duplication strengthens checking.  Not a
        * strong reason, but sufficient in the absence of others.
        * [Now we resolve ties in favor of the earlier string if
        * it happens that c_offset_min has been invalidated, since the
        * earlier string may buy us something the later one won't.]
        */
        minlen = 0;

        data.longest_fixed = newSVpvs("");
        data.longest_float = newSVpvs("");
        data.last_found = newSVpvs("");
        data.longest = &(data.longest_fixed);
        first = scan;
        if (!r->regstclass) {
            cl_init(pRExC_state, &ch_class);
            data.start_class = &ch_class;
            stclass_flag = SCF_DO_STCLASS_AND;
        } else                          /* XXXX Check for BOUND? */
            stclass_flag = 0;
        data.last_closep = &last_close;

        minlen = study_chunk(pRExC_state, &first, &fake, scan + RExC_size, /* Up to end */
                             &data, SCF_DO_SUBSTR | SCF_WHILEM_VISITED_POS | stclass_flag);
        if ( RExC_npar == 1 && data.longest == &(data.longest_fixed)
             && data.last_start_min == 0 && data.last_end > 0
             && !RExC_seen_zerolen
             && (!(RExC_seen & REG_SEEN_GPOS) || (r->reganch & ROPT_ANCH_GPOS)))
            r->reganch |= ROPT_CHECK_ALL;
        scan_commit(pRExC_state, &data);
        SvREFCNT_dec(data.last_found);

        longest_float_length = CHR_SVLEN(data.longest_float);
        if (longest_float_length
            || (data.flags & SF_FL_BEFORE_EOL
                && (!(data.flags & SF_FL_BEFORE_MEOL)
                    || (RExC_flags & PMf_MULTILINE)))) {
            int t;

            if (SvCUR(data.longest_fixed)                       /* ok to leave SvCUR */
                && data.offset_fixed == data.offset_float_min
                && SvCUR(data.longest_fixed) == SvCUR(data.longest_float))
                    goto remove_float;          /* As in (a)+. */

            if (SvUTF8(data.longest_float)) {
                r->float_utf8 = data.longest_float;
                r->float_substr = NULL;
            } else {
                r->float_substr = data.longest_float;
                r->float_utf8 = NULL;
            }
            r->float_min_offset = data.offset_float_min;
            r->float_max_offset = data.offset_float_max;
            t = (data.flags & SF_FL_BEFORE_EOL /* Can't have SEOL and MULTI */
                       && (!(data.flags & SF_FL_BEFORE_MEOL)
                           || (RExC_flags & PMf_MULTILINE)));
            fbm_compile(data.longest_float, t ? FBMcf_TAIL : 0);
        }
        else {
          remove_float:
            r->float_substr = r->float_utf8 = NULL;
            SvREFCNT_dec(data.longest_float);
            longest_float_length = 0;
        }

        longest_fixed_length = CHR_SVLEN(data.longest_fixed);
        if (longest_fixed_length
            || (data.flags & SF_FIX_BEFORE_EOL /* Cannot have SEOL and MULTI */
                && (!(data.flags & SF_FIX_BEFORE_MEOL)
                    || (RExC_flags & PMf_MULTILINE)))) {
            int t;

            if (SvUTF8(data.longest_fixed)) {
                r->anchored_utf8 = data.longest_fixed;
                r->anchored_substr = NULL;
            } else {
                r->anchored_substr = data.longest_fixed;
                r->anchored_utf8 = NULL;
            }
            r->anchored_offset = data.offset_fixed;
            t = (data.flags & SF_FIX_BEFORE_EOL /* Can't have SEOL and MULTI */
                 && (!(data.flags & SF_FIX_BEFORE_MEOL)
                     || (RExC_flags & PMf_MULTILINE)));
            fbm_compile(data.longest_fixed, t ? FBMcf_TAIL : 0);
        }
        else {
            r->anchored_substr = r->anchored_utf8 = NULL;
            SvREFCNT_dec(data.longest_fixed);
            longest_fixed_length = 0;
        }
        if (r->regstclass
            && (OP(r->regstclass) == REG_ANY || OP(r->regstclass) == SANY))
            r->regstclass = NULL;
        if ((!(r->anchored_substr || r->anchored_utf8) || r->anchored_offset)
            && stclass_flag
            && !(data.start_class->flags & ANYOF_EOS)
            && !cl_is_anything(data.start_class))
        {
            const U32 n = add_data(pRExC_state, 1, "f");

            Newx(RExC_rx->data->data[n], 1,
                struct regnode_charclass_class);
            StructCopy(data.start_class,
                       (struct regnode_charclass_class*)RExC_rx->data->data[n],
                       struct regnode_charclass_class);
            r->regstclass = (regnode*)RExC_rx->data->data[n];
            r->reganch &= ~ROPT_SKIP;   /* Used in find_byclass(). */
            PL_regdata = r->data; /* for regprop() */
            DEBUG_r({ SV *sv = sv_newmortal();
                      regprop(sv, (regnode*)data.start_class);
                      PerlIO_printf(Perl_debug_log,
                                    "synthetic stclass \"%s\".\n",
                                    SvPVX_const(sv));});
        }

        /* A temporary algorithm prefers floated substr to fixed one to dig more info. */
        if (longest_fixed_length > longest_float_length) {
            r->check_substr = r->anchored_substr;
            r->check_utf8 = r->anchored_utf8;
            r->check_offset_min = r->check_offset_max = r->anchored_offset;
            if (r->reganch & ROPT_ANCH_SINGLE)
                r->reganch |= ROPT_NOSCAN;
        }
        else {
            r->check_substr = r->float_substr;
            r->check_utf8 = r->float_utf8;
            r->check_offset_min = data.offset_float_min;
            r->check_offset_max = data.offset_float_max;
        }
        /* XXXX Currently intuiting is not compatible with ANCH_GPOS.
           This should be changed ASAP!  */
        if ((r->check_substr || r->check_utf8) && !(r->reganch & ROPT_ANCH_GPOS)) {
            r->reganch |= RE_USE_INTUIT;
            if (SvTAIL(r->check_substr ? r->check_substr : r->check_utf8))
                r->reganch |= RE_INTUIT_TAIL;
        }
    }
    else {
        /* Several toplevels. Best we can is to set minlen. */
        I32 fake;
        struct regnode_charclass_class ch_class;
        I32 last_close = 0;
        
        DEBUG_r(PerlIO_printf(Perl_debug_log, "\n"));
        scan = r->program + 1;
        cl_init(pRExC_state, &ch_class);
        data.start_class = &ch_class;
        data.last_closep = &last_close;
        minlen = study_chunk(pRExC_state, &scan, &fake, scan + RExC_size, &data, SCF_DO_STCLASS_AND|SCF_WHILEM_VISITED_POS);
        r->check_substr = r->check_utf8 = r->anchored_substr = r->anchored_utf8
                = r->float_substr = r->float_utf8 = NULL;
        if (!(data.start_class->flags & ANYOF_EOS)
            && !cl_is_anything(data.start_class))
        {
            const U32 n = add_data(pRExC_state, 1, "f");

            Newx(RExC_rx->data->data[n], 1,
                struct regnode_charclass_class);
            StructCopy(data.start_class,
                       (struct regnode_charclass_class*)RExC_rx->data->data[n],
                       struct regnode_charclass_class);
            r->regstclass = (regnode*)RExC_rx->data->data[n];
            r->reganch &= ~ROPT_SKIP;   /* Used in find_byclass(). */
            DEBUG_r({ SV* sv = sv_newmortal();
                      regprop(sv, (regnode*)data.start_class);
                      PerlIO_printf(Perl_debug_log,
                                    "synthetic stclass \"%s\".\n",
                                    SvPVX_const(sv));});
        }
    }

    r->minlen = minlen;
    if (RExC_seen & REG_SEEN_GPOS)
        r->reganch |= ROPT_GPOS_SEEN;
    if (RExC_seen & REG_SEEN_LOOKBEHIND)
        r->reganch |= ROPT_LOOKBEHIND_SEEN;
    if (RExC_seen & REG_SEEN_EVAL)
        r->reganch |= ROPT_EVAL_SEEN;
    if (RExC_seen & REG_SEEN_CANY)
        r->reganch |= ROPT_CANY_SEEN;
    Newxz(r->startp, RExC_npar, I32);
    Newxz(r->endp, RExC_npar, I32);
    PL_regdata = r->data; /* for regprop() */
    DEBUG_r(regdump(r));
    return(r);
}

/*
 - reg - regular expression, i.e. main body or parenthesized thing
 *
 * Caller must absorb opening parenthesis.
 *
 * Combining parenthesis handling with the base level of regular expression
 * is a trifle forced, but the need to tie the tails of the branches to what
 * follows makes it hard to avoid.
 */
STATIC regnode *
S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp)
    /* paren: Parenthesized? 0=top, 1=(, inside: changed to letter. */
{
    register regnode *ret;              /* Will be the head of the group. */
    register regnode *br;
    register regnode *lastbr;
    register regnode *ender = NULL;
    register I32 parno = 0;
    I32 flags;
    const I32 oregflags = RExC_flags;
    bool have_branch = 0;
    bool is_open = 0;

    /* for (?g), (?gc), and (?o) warnings; warning
       about (?c) will warn about (?g) -- japhy    */

#define WASTED_O  0x01
#define WASTED_G  0x02
#define WASTED_C  0x04
#define WASTED_GC (0x02|0x04)
    I32 wastedflags = 0x00;

    char * parse_start = RExC_parse; /* MJD */
    char * const oregcomp_parse = RExC_parse;

    *flagp = 0;                         /* Tentatively. */


    /* Make an OPEN node, if parenthesized. */
    if (paren) {
        if (*RExC_parse == '?') { /* (?...) */
            U32 posflags = 0, negflags = 0;
            U32 *flagsp = &posflags;
            bool is_logical = 0;
            const char * const seqstart = RExC_parse;

            RExC_parse++;
            paren = *RExC_parse++;
            ret = NULL;                 /* For look-ahead/behind. */
            switch (paren) {
            case '<':           /* (?<...) */
                RExC_seen |= REG_SEEN_LOOKBEHIND;
                if (*RExC_parse == '!')
                    paren = ',';
                if (*RExC_parse != '=' && *RExC_parse != '!')
                    goto unknown;
                RExC_parse++;
            case '=':           /* (?=...) */
            case '!':           /* (?!...) */
                RExC_seen_zerolen++;
            case ':':           /* (?:...) */
            case '>':           /* (?>...) */
                break;
            case '$':           /* (?$...) */
            case '@':           /* (?@...) */
                vFAIL2("Sequence (?%c...) not implemented", (int)paren);
                break;
            case '#':           /* (?#...) */
                while (*RExC_parse && *RExC_parse != ')')
                    RExC_parse++;
                if (*RExC_parse != ')')
                    FAIL("Sequence (?#... not terminated");
                nextchar(pRExC_state);
                *flagp = TRYAGAIN;
                return NULL;
            case 'p':           /* (?p...) */
                if (SIZE_ONLY && ckWARN2(WARN_DEPRECATED, WARN_REGEXP))
                    vWARNdep(RExC_parse, "(?p{}) is deprecated - use (??{})");
                /* FALL THROUGH*/
            case '?':           /* (??...) */
                is_logical = 1;
                if (*RExC_parse != '{')
                    goto unknown;
                paren = *RExC_parse++;
                /* FALL THROUGH */
            case '{':           /* (?{...}) */
            {
                I32 count = 1;
                U32 n = 0;
                char c;
                char *s = RExC_parse;

                RExC_seen_zerolen++;
                RExC_seen |= REG_SEEN_EVAL;
                while (count && (c = *RExC_parse)) {
                    if (c == '\\') {
                        if (RExC_parse[1])
                            RExC_parse++;
                    }
                    else if (c == '{')
                        count++;
                    else if (c == '}')
                        count--;
                    RExC_parse++;
                }
                if (*RExC_parse != ')') {
                    RExC_parse = s;             
                    vFAIL("Sequence (?{...}) not terminated or not {}-balanced");
                }
                if (!SIZE_ONLY) {
                    PAD *pad;
                    OP_4tree *sop, *rop;
                    SV * const sv = newSVpvn(s, RExC_parse - 1 - s);

                    ENTER;
                    Perl_save_re_context(aTHX);
                    rop = sv_compile_2op(sv, &sop, "re", &pad);
                    sop->op_private |= OPpREFCOUNTED;
                    /* re_dup will OpREFCNT_inc */
                    OpREFCNT_set(sop, 1);
                    LEAVE;

                    n = add_data(pRExC_state, 3, "nop");
                    RExC_rx->data->data[n] = (void*)rop;
                    RExC_rx->data->data[n+1] = (void*)sop;
                    RExC_rx->data->data[n+2] = (void*)pad;
                    SvREFCNT_dec(sv);
                }
                else {                                          /* First pass */
                    if (PL_reginterp_cnt < ++RExC_seen_evals
                        && IN_PERL_RUNTIME)
                        /* No compiled RE interpolated, has runtime
                           components ===> unsafe.  */
                        FAIL("Eval-group not allowed at runtime, use re 'eval'");
                    if (PL_tainting && PL_tainted)
                        FAIL("Eval-group in insecure regular expression");
                }
                
                nextchar(pRExC_state);
                if (is_logical) {
                    ret = reg_node(pRExC_state, LOGICAL);
                    if (!SIZE_ONLY)
                        ret->flags = 2;
                    regtail(pRExC_state, ret, reganode(pRExC_state, EVAL, n));
                    /* deal with the length of this later - MJD */
                    return ret;
                }
                ret = reganode(pRExC_state, EVAL, n);
                Set_Node_Length(ret, RExC_parse - parse_start + 1);
                Set_Node_Offset(ret, parse_start);
                return ret;
            }
            case '(':           /* (?(?{...})...) and (?(?=...)...) */
            {
                if (RExC_parse[0] == '?') {        /* (?(?...)) */
                    if (RExC_parse[1] == '=' || RExC_parse[1] == '!'
                        || RExC_parse[1] == '<'
                        || RExC_parse[1] == '{') { /* Lookahead or eval. */
                        I32 flag;
                        
                        ret = reg_node(pRExC_state, LOGICAL);
                        if (!SIZE_ONLY)
                            ret->flags = 1;
                        regtail(pRExC_state, ret, reg(pRExC_state, 1, &flag));
                        goto insert_if;
                    }
                }
                else if (RExC_parse[0] >= '1' && RExC_parse[0] <= '9' ) {
                    /* (?(1)...) */
                    char c;
                    parno = atoi(RExC_parse++);

                    while (isDIGIT(*RExC_parse))
                        RExC_parse++;
                    ret = reganode(pRExC_state, GROUPP, parno);

                    if ((c = *nextchar(pRExC_state)) != ')')
                        vFAIL("Switch condition not recognized");
                  insert_if:
                    regtail(pRExC_state, ret, reganode(pRExC_state, IFTHEN, 0));
                    br = regbranch(pRExC_state, &flags, 1);
                    if (br == NULL)
                        br = reganode(pRExC_state, LONGJMP, 0);
                    else
                        regtail(pRExC_state, br, reganode(pRExC_state, LONGJMP, 0));
                    c = *nextchar(pRExC_state);
                    if (flags&HASWIDTH)
                        *flagp |= HASWIDTH;
                    if (c == '|') {
                        lastbr = reganode(pRExC_state, IFTHEN, 0); /* Fake one for optimizer. */
                        regbranch(pRExC_state, &flags, 1);
                        regtail(pRExC_state, ret, lastbr);
                        if (flags&HASWIDTH)
                            *flagp |= HASWIDTH;
                        c = *nextchar(pRExC_state);
                    }
                    else
                        lastbr = NULL;
                    if (c != ')')
                        vFAIL("Switch (?(condition)... contains too many branches");
                    ender = reg_node(pRExC_state, TAIL);
                    regtail(pRExC_state, br, ender);
                    if (lastbr) {
                        regtail(pRExC_state, lastbr, ender);
                        regtail(pRExC_state, NEXTOPER(NEXTOPER(lastbr)), ender);
                    }
                    else
                        regtail(pRExC_state, ret, ender);
                    return ret;
                }
                else {
                    vFAIL2("Unknown switch condition (?(%.2s", RExC_parse);
                }
            }
            case 0:
                RExC_parse--; /* for vFAIL to print correctly */
                vFAIL("Sequence (? incomplete");
                break;
            default:
                --RExC_parse;
              parse_flags:      /* (?i) */
                while (*RExC_parse && strchr("iogcmsx", *RExC_parse)) {
                    /* (?g), (?gc) and (?o) are useless here
                       and must be globally applied -- japhy */

                    if (*RExC_parse == 'o' || *RExC_parse == 'g') {
                        if (SIZE_ONLY && ckWARN(WARN_REGEXP)) {
                            const I32 wflagbit = *RExC_parse == 'o' ? WASTED_O : WASTED_G;
                            if (! (wastedflags & wflagbit) ) {
                                wastedflags |= wflagbit;
                                vWARN5(
                                    RExC_parse + 1,
                                    "Useless (%s%c) - %suse /%c modifier",
                                    flagsp == &negflags ? "?-" : "?",
                                    *RExC_parse,
                                    flagsp == &negflags ? "don't " : "",
                                    *RExC_parse
                                );
                            }
                        }
                    }
                    else if (*RExC_parse == 'c') {
                        if (SIZE_ONLY && ckWARN(WARN_REGEXP)) {
                            if (! (wastedflags & WASTED_C) ) {
                                wastedflags |= WASTED_GC;
                                vWARN3(
                                    RExC_parse + 1,
                                    "Useless (%sc) - %suse /gc modifier",
                                    flagsp == &negflags ? "?-" : "?",
                                    flagsp == &negflags ? "don't " : ""
                                );
                            }
                        }
                    }
                    else { pmflag(flagsp, *RExC_parse); }

                    ++RExC_parse;
                }
                if (*RExC_parse == '-') {
                    flagsp = &negflags;
                    wastedflags = 0;  /* reset so (?g-c) warns twice */
                    ++RExC_parse;
                    goto parse_flags;
                }
                RExC_flags |= posflags;
                RExC_flags &= ~negflags;
                if (*RExC_parse == ':') {
                    RExC_parse++;
                    paren = ':';
                    break;
                }               
              unknown:
                if (*RExC_parse != ')') {
                    RExC_parse++;
                    vFAIL3("Sequence (%.*s...) not recognized", RExC_parse-seqstart, seqstart);
                }
                nextchar(pRExC_state);
                *flagp = TRYAGAIN;
                return NULL;
            }
        }
        else {                  /* (...) */
            parno = RExC_npar;
            RExC_npar++;
            ret = reganode(pRExC_state, OPEN, parno);
            Set_Node_Length(ret, 1); /* MJD */
            Set_Node_Offset(ret, RExC_parse); /* MJD */
            is_open = 1;
        }
    }
    else                        /* ! paren */
        ret = NULL;

    /* Pick up the branches, linking them together. */
    parse_start = RExC_parse;   /* MJD */
    br = regbranch(pRExC_state, &flags, 1);
    /*     branch_len = (paren != 0); */

    if (br == NULL)
        return(NULL);
    if (*RExC_parse == '|') {
        if (!SIZE_ONLY && RExC_extralen) {
            reginsert(pRExC_state, BRANCHJ, br);
        }
        else {                  /* MJD */
            reginsert(pRExC_state, BRANCH, br);
            Set_Node_Length(br, paren != 0);
            Set_Node_Offset_To_R(br-RExC_emit_start, parse_start-RExC_start);
        }
        have_branch = 1;
        if (SIZE_ONLY)
            RExC_extralen += 1;         /* For BRANCHJ-BRANCH. */
    }
    else if (paren == ':') {
        *flagp |= flags&SIMPLE;
    }
    if (is_open) {                              /* Starts with OPEN. */
        regtail(pRExC_state, ret, br);          /* OPEN -> first. */
    }
    else if (paren != '?')              /* Not Conditional */
        ret = br;
    *flagp |= flags & (SPSTART | HASWIDTH);
    lastbr = br;
    while (*RExC_parse == '|') {
        if (!SIZE_ONLY && RExC_extralen) {
            ender = reganode(pRExC_state, LONGJMP,0);
            regtail(pRExC_state, NEXTOPER(NEXTOPER(lastbr)), ender); /* Append to the previous. */
        }
        if (SIZE_ONLY)
            RExC_extralen += 2;         /* Account for LONGJMP. */
        nextchar(pRExC_state);
        br = regbranch(pRExC_state, &flags, 0);

        if (br == NULL)
            return(NULL);
        regtail(pRExC_state, lastbr, br);               /* BRANCH -> BRANCH. */
        lastbr = br;
        if (flags&HASWIDTH)
            *flagp |= HASWIDTH;
        *flagp |= flags&SPSTART;
    }

    if (have_branch || paren != ':') {
        /* Make a closing node, and hook it on the end. */
        switch (paren) {
        case ':':
            ender = reg_node(pRExC_state, TAIL);
            break;
        case 1:
            ender = reganode(pRExC_state, CLOSE, parno);
            Set_Node_Offset(ender,RExC_parse+1); /* MJD */
            Set_Node_Length(ender,1); /* MJD */
            break;
        case '<':
        case ',':
        case '=':
        case '!':
            *flagp &= ~HASWIDTH;
            /* FALL THROUGH */
        case '>':
            ender = reg_node(pRExC_state, SUCCEED);
            break;
        case 0:
            ender = reg_node(pRExC_state, END);
            break;
        }
        regtail(pRExC_state, lastbr, ender);

        if (have_branch && !SIZE_ONLY) {
            /* Hook the tails of the branches to the closing node. */
            for (br = ret; br; br = regnext(br)) {
                const U8 op = PL_regkind[OP(br)];
                if (op == BRANCH) {
                    regtail(pRExC_state, NEXTOPER(br), ender);
                }
                else if (op == BRANCHJ) {
                    regtail(pRExC_state, NEXTOPER(NEXTOPER(br)), ender);
                }
            }
        }
    }

    {
        const char *p;
        static const char parens[] = "=!<,>";

        if (paren && (p = strchr(parens, paren))) {
            U8 node = ((p - parens) % 2) ? UNLESSM : IFMATCH;
            int flag = (p - parens) > 1;

            if (paren == '>')
                node = SUSPEND, flag = 0;
            reginsert(pRExC_state, node,ret);
            Set_Node_Cur_Length(ret);
            Set_Node_Offset(ret, parse_start + 1);
            ret->flags = flag;
            regtail(pRExC_state, ret, reg_node(pRExC_state, TAIL));
        }
    }

    /* Check for proper termination. */
    if (paren) {
        RExC_flags = oregflags;
        if (RExC_parse >= RExC_end || *nextchar(pRExC_state) != ')') {
            RExC_parse = oregcomp_parse;
            vFAIL("Unmatched (");
        }
    }
    else if (!paren && RExC_parse < RExC_end) {
        if (*RExC_parse == ')') {
            RExC_parse++;
            vFAIL("Unmatched )");
        }
        else
            FAIL("Junk on end of regexp");      /* "Can't happen". */
        /* NOTREACHED */
    }

    return(ret);
}

/*
 - regbranch - one alternative of an | operator
 *
 * Implements the concatenation operator.
 */
STATIC regnode *
S_regbranch(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, I32 first)
{
    register regnode *ret;
    register regnode *chain = NULL;
    register regnode *latest;
    I32 flags = 0, c = 0;

    if (first)
        ret = NULL;
    else {
        if (!SIZE_ONLY && RExC_extralen)
            ret = reganode(pRExC_state, BRANCHJ,0);
        else {
            ret = reg_node(pRExC_state, BRANCH);
            Set_Node_Length(ret, 1);
        }
    }
        
    if (!first && SIZE_ONLY)
        RExC_extralen += 1;                     /* BRANCHJ */

    *flagp = WORST;                     /* Tentatively. */

    RExC_parse--;
    nextchar(pRExC_state);
    while (RExC_parse < RExC_end && *RExC_parse != '|' && *RExC_parse != ')') {
        flags &= ~TRYAGAIN;
        latest = regpiece(pRExC_state, &flags);
        if (latest == NULL) {
            if (flags & TRYAGAIN)
                continue;
            return(NULL);
        }
        else if (ret == NULL)
            ret = latest;
        *flagp |= flags&HASWIDTH;
        if (chain == NULL)      /* First piece. */
            *flagp |= flags&SPSTART;
        else {
            RExC_naughty++;
            regtail(pRExC_state, chain, latest);
        }
        chain = latest;
        c++;
    }
    if (chain == NULL) {        /* Loop ran zero times. */
        chain = reg_node(pRExC_state, NOTHING);
        if (ret == NULL)
            ret = chain;
    }
    if (c == 1) {
        *flagp |= flags&SIMPLE;
    }

    return ret;
}

/*
 - regpiece - something followed by possible [*+?]
 *
 * Note that the branching code sequences used for ? and the general cases
 * of * and + are somewhat optimized:  they use the same NOTHING node as
 * both the endmarker for their branch list and the body of the last branch.
 * It might seem that this node could be dispensed with entirely, but the
 * endmarker role is not redundant.
 */
STATIC regnode *
S_regpiece(pTHX_ RExC_state_t *pRExC_state, I32 *flagp)
{
    register regnode *ret;
    register char op;
    register char *next;
    I32 flags;
    const char * const origparse = RExC_parse;
    I32 min;
    I32 max = REG_INFTY;
    char *parse_start;
    const char *maxpos = NULL;

    ret = regatom(pRExC_state, &flags);
    if (ret == NULL) {
        if (flags & TRYAGAIN)
            *flagp |= TRYAGAIN;
        return(NULL);
    }

    op = *RExC_parse;

    if (op == '{' && regcurly(RExC_parse)) {
        parse_start = RExC_parse; /* MJD */
        next = RExC_parse + 1;
        maxpos = NULL;
        while (isDIGIT(*next) || *next == ',') {
            if (*next == ',') {
                if (maxpos)
                    break;
                else
                    maxpos = next;
            }
            next++;
        }
        if (*next == '}') {             /* got one */
            if (!maxpos)
                maxpos = next;
            RExC_parse++;
            min = atoi(RExC_parse);
            if (*maxpos == ',')
                maxpos++;
            else
                maxpos = RExC_parse;
            max = atoi(maxpos);
            if (!max && *maxpos != '0')
                max = REG_INFTY;                /* meaning "infinity" */
            else if (max >= REG_INFTY)
                vFAIL2("Quantifier in {,} bigger than %d", REG_INFTY - 1);
            RExC_parse = next;
            nextchar(pRExC_state);

        do_curly:
            if ((flags&SIMPLE)) {
                RExC_naughty += 2 + RExC_naughty / 2;
                reginsert(pRExC_state, CURLY, ret);
                Set_Node_Offset(ret, parse_start+1); /* MJD */
                Set_Node_Cur_Length(ret);
            }
            else {
                regnode *w = reg_node(pRExC_state, WHILEM);

                w->flags = 0;
                regtail(pRExC_state, ret, w);
                if (!SIZE_ONLY && RExC_extralen) {
                    reginsert(pRExC_state, LONGJMP,ret);
                    reginsert(pRExC_state, NOTHING,ret);
                    NEXT_OFF(ret) = 3;  /* Go over LONGJMP. */
                }
                reginsert(pRExC_state, CURLYX,ret);
                                /* MJD hk */
                Set_Node_Offset(ret, parse_start+1);
                Set_Node_Length(ret,
                                op == '{' ? (RExC_parse - parse_start) : 1);

                if (!SIZE_ONLY && RExC_extralen)
                    NEXT_OFF(ret) = 3;  /* Go over NOTHING to LONGJMP. */
                regtail(pRExC_state, ret, reg_node(pRExC_state, NOTHING));
                if (SIZE_ONLY)
                    RExC_whilem_seen++, RExC_extralen += 3;
                RExC_naughty += 4 + RExC_naughty;       /* compound interest */
            }
            ret->flags = 0;

            if (min > 0)
                *flagp = WORST;
            if (max > 0)
                *flagp |= HASWIDTH;
            if (max && max < min)
                vFAIL("Can't do {n,m} with n > m");
            if (!SIZE_ONLY) {
                ARG1_SET(ret, (U16)min);
                ARG2_SET(ret, (U16)max);
            }

            goto nest_check;
        }
    }

    if (!ISMULT1(op)) {
        *flagp = flags;
        return(ret);
    }

#if 0                           /* Now runtime fix should be reliable. */

    /* if this is reinstated, don't forget to put this back into perldiag:

            =item Regexp *+ operand could be empty at {#} in regex m/%s/

           (F) The part of the regexp subject to either the * or + quantifier
           could match an empty string. The {#} shows in the regular
           expression about where the problem was discovered.

    */

    if (!(flags&HASWIDTH) && op != '?')
      vFAIL("Regexp *+ operand could be empty");
#endif

    parse_start = RExC_parse;
    nextchar(pRExC_state);

    *flagp = (op != '+') ? (WORST|SPSTART|HASWIDTH) : (WORST|HASWIDTH);

    if (op == '*' && (flags&SIMPLE)) {
        reginsert(pRExC_state, STAR, ret);
        ret->flags = 0;
        RExC_naughty += 4;
    }
    else if (op == '*') {
        min = 0;
        goto do_curly;
    }
    else if (op == '+' && (flags&SIMPLE)) {
        reginsert(pRExC_state, PLUS, ret);
        ret->flags = 0;
        RExC_naughty += 3;
    }
    else if (op == '+') {
        min = 1;
        goto do_curly;
    }
    else if (op == '?') {
        min = 0; max = 1;
        goto do_curly;
    }
  nest_check:
    if (!SIZE_ONLY && !(flags&HASWIDTH) && max > REG_INFTY/3 && ckWARN(WARN_REGEXP)) {
        vWARN3(RExC_parse,
               "%.*s matches null string many times",
               (int)(RExC_parse >= origparse ? RExC_parse - origparse : 0),
               origparse);
    }

    if (*RExC_parse == '?') {
        nextchar(pRExC_state);
        reginsert(pRExC_state, MINMOD, ret);
        regtail(pRExC_state, ret, ret + NODE_STEP_REGNODE);
    }
    if (ISMULT2(RExC_parse)) {
        RExC_parse++;
        vFAIL("Nested quantifiers");
    }

    return(ret);
}

/*
 - regatom - the lowest level
 *
 * Optimization:  gobbles an entire sequence of ordinary characters so that
 * it can turn them into a single node, which is smaller to store and
 * faster to run.  Backslashed characters are exceptions, each becoming a
 * separate node; the code is simpler that way and it's not worth fixing.
 *
 * [Yes, it is worth fixing, some scripts can run twice the speed.] */
STATIC regnode *
S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp)
{
    register regnode *ret = NULL;
    I32 flags;
    char *parse_start = RExC_parse;

    *flagp = WORST;             /* Tentatively. */

tryagain:
    switch (*RExC_parse) {
    case '^':
        RExC_seen_zerolen++;
        nextchar(pRExC_state);
        if (RExC_flags & PMf_MULTILINE)
            ret = reg_node(pRExC_state, MBOL);
        else if (RExC_flags & PMf_SINGLELINE)
            ret = reg_node(pRExC_state, SBOL);
        else
            ret = reg_node(pRExC_state, BOL);
        Set_Node_Length(ret, 1); /* MJD */
        break;
    case '$':
        nextchar(pRExC_state);
        if (*RExC_parse)
            RExC_seen_zerolen++;
        if (RExC_flags & PMf_MULTILINE)
            ret = reg_node(pRExC_state, MEOL);
        else if (RExC_flags & PMf_SINGLELINE)
            ret = reg_node(pRExC_state, SEOL);
        else
            ret = reg_node(pRExC_state, EOL);
        Set_Node_Length(ret, 1); /* MJD */
        break;
    case '.':
        nextchar(pRExC_state);
        if (RExC_flags & PMf_SINGLELINE)
            ret = reg_node(pRExC_state, SANY);
        else
            ret = reg_node(pRExC_state, REG_ANY);
        *flagp |= HASWIDTH|SIMPLE;
        RExC_naughty++;
        Set_Node_Length(ret, 1); /* MJD */
        break;
    case '[':
    {
        char *oregcomp_parse = ++RExC_parse;
        ret = regclass(pRExC_state);
        if (*RExC_parse != ']') {
            RExC_parse = oregcomp_parse;
            vFAIL("Unmatched [");
        }
        nextchar(pRExC_state);
        *flagp |= HASWIDTH|SIMPLE;
        Set_Node_Length(ret, RExC_parse - oregcomp_parse + 1); /* MJD */
        break;
    }
    case '(':
        nextchar(pRExC_state);
        ret = reg(pRExC_state, 1, &flags);
        if (ret == NULL) {
                if (flags & TRYAGAIN) {
                    if (RExC_parse == RExC_end) {
                         /* Make parent create an empty node if needed. */
                        *flagp |= TRYAGAIN;
                        return(NULL);
                    }
                    goto tryagain;
                }
                return(NULL);
        }
        *flagp |= flags&(HASWIDTH|SPSTART|SIMPLE);
        break;
    case '|':
    case ')':
        if (flags & TRYAGAIN) {
            *flagp |= TRYAGAIN;
            return NULL;
        }
        vFAIL("Internal urp");
                                /* Supposed to be caught earlier. */
        break;
    case '{':
        if (!regcurly(RExC_parse)) {
            RExC_parse++;
            goto defchar;
        }
        /* FALL THROUGH */
    case '?':
    case '+':
    case '*':
        RExC_parse++;
        vFAIL("Quantifier follows nothing");
        break;
    case '\\':
        switch (*++RExC_parse) {
        case 'A':
            RExC_seen_zerolen++;
            ret = reg_node(pRExC_state, SBOL);
            *flagp |= SIMPLE;
            nextchar(pRExC_state);
            Set_Node_Length(ret, 2); /* MJD */
            break;
        case 'G':
            ret = reg_node(pRExC_state, GPOS);
            RExC_seen |= REG_SEEN_GPOS;
            *flagp |= SIMPLE;
            nextchar(pRExC_state);
            Set_Node_Length(ret, 2); /* MJD */
            break;
        case 'Z':
            ret = reg_node(pRExC_state, SEOL);
            *flagp |= SIMPLE;
            RExC_seen_zerolen++;                /* Do not optimize RE away */
            nextchar(pRExC_state);
            break;
        case 'z':
            ret = reg_node(pRExC_state, EOS);
            *flagp |= SIMPLE;
            RExC_seen_zerolen++;                /* Do not optimize RE away */
            nextchar(pRExC_state);
            Set_Node_Length(ret, 2); /* MJD */
            break;
        case 'C':
            ret = reg_node(pRExC_state, CANY);
            RExC_seen |= REG_SEEN_CANY;
            *flagp |= HASWIDTH|SIMPLE;
            nextchar(pRExC_state);
            Set_Node_Length(ret, 2); /* MJD */
            break;
        case 'X':
            ret = reg_node(pRExC_state, CLUMP);
            *flagp |= HASWIDTH;
            nextchar(pRExC_state);
            Set_Node_Length(ret, 2); /* MJD */
            break;
        case 'w':
            ret = reg_node(pRExC_state, (U8)(LOC ? ALNUML     : ALNUM));
            *flagp |= HASWIDTH|SIMPLE;
            nextchar(pRExC_state);
            Set_Node_Length(ret, 2); /* MJD */
            break;
        case 'W':
            ret = reg_node(pRExC_state, (U8)(LOC ? NALNUML    : NALNUM));
            *flagp |= HASWIDTH|SIMPLE;
            nextchar(pRExC_state);
            Set_Node_Length(ret, 2); /* MJD */
            break;
        case 'b':
            RExC_seen_zerolen++;
            RExC_seen |= REG_SEEN_LOOKBEHIND;
            ret = reg_node(pRExC_state, (U8)(LOC ? BOUNDL     : BOUND));
            *flagp |= SIMPLE;
            nextchar(pRExC_state);
            Set_Node_Length(ret, 2); /* MJD */
            break;
        case 'B':
            RExC_seen_zerolen++;
            RExC_seen |= REG_SEEN_LOOKBEHIND;
            ret = reg_node(pRExC_state, (U8)(LOC ? NBOUNDL    : NBOUND));
            *flagp |= SIMPLE;
            nextchar(pRExC_state);
            Set_Node_Length(ret, 2); /* MJD */
            break;
        case 's':
            ret = reg_node(pRExC_state, (U8)(LOC ? SPACEL     : SPACE));
            *flagp |= HASWIDTH|SIMPLE;
            nextchar(pRExC_state);
            Set_Node_Length(ret, 2); /* MJD */
            break;
        case 'S':
            ret = reg_node(pRExC_state, (U8)(LOC ? NSPACEL    : NSPACE));
            *flagp |= HASWIDTH|SIMPLE;
            nextchar(pRExC_state);
            Set_Node_Length(ret, 2); /* MJD */
            break;
        case 'd':
            ret = reg_node(pRExC_state, DIGIT);
            *flagp |= HASWIDTH|SIMPLE;
            nextchar(pRExC_state);
            Set_Node_Length(ret, 2); /* MJD */
            break;
        case 'D':
            ret = reg_node(pRExC_state, NDIGIT);
            *flagp |= HASWIDTH|SIMPLE;
            nextchar(pRExC_state);
            Set_Node_Length(ret, 2); /* MJD */
            break;
        case 'p':
        case 'P':
            {   
                char* oldregxend = RExC_end;
                char* parse_start = RExC_parse - 2;

                if (RExC_parse[1] == '{') {
                  /* a lovely hack--pretend we saw [\pX] instead */
                    RExC_end = strchr(RExC_parse, '}');
                    if (!RExC_end) {
                        U8 c = (U8)*RExC_parse;
                        RExC_parse += 2;
                        RExC_end = oldregxend;
                        vFAIL2("Missing right brace on \\%c{}", c);
                    }
                    RExC_end++;
                }
                else {
                    RExC_end = RExC_parse + 2;
                    if (RExC_end > oldregxend)
                        RExC_end = oldregxend;
                }
                RExC_parse--;

                ret = regclass(pRExC_state);

                RExC_end = oldregxend;
                RExC_parse--;

                Set_Node_Offset(ret, parse_start + 2);
                Set_Node_Cur_Length(ret);
                nextchar(pRExC_state);
                *flagp |= HASWIDTH|SIMPLE;
            }
            break;
        case 'n':
        case 'r':
        case 't':
        case 'f':
        case 'e':
        case 'a':
        case 'x':
        case 'c':
        case '0':
            goto defchar;
        case '1': case '2': case '3': case '4':
        case '5': case '6': case '7': case '8': case '9':
            {
                const I32 num = atoi(RExC_parse);

                if (num > 9 && num >= RExC_npar)
                    goto defchar;
                else {
                    char * parse_start = RExC_parse - 1; /* MJD */
                    while (isDIGIT(*RExC_parse))
                        RExC_parse++;

                    if (!SIZE_ONLY && num > (I32)RExC_rx->nparens)
                        vFAIL("Reference to nonexistent group");
                    RExC_sawback = 1;
                    ret = reganode(pRExC_state,
                                   (U8)(FOLD ? (LOC ? REFFL : REFF) : REF),
                                   num);
                    *flagp |= HASWIDTH;

                    /* override incorrect value set in reganode MJD */
                    Set_Node_Offset(ret, parse_start+1);
                    Set_Node_Cur_Length(ret); /* MJD */
                    RExC_parse--;
                    nextchar(pRExC_state);
                }
            }
            break;
        case '\0':
            if (RExC_parse >= RExC_end)
                FAIL("Trailing \\");
            /* FALL THROUGH */
        default:
            /* Do not generate "unrecognized" warnings here, we fall
               back into the quick-grab loop below */
            parse_start--;
            goto defchar;
        }
        break;

    case '#':
        if (RExC_flags & PMf_EXTENDED) {
            while (RExC_parse < RExC_end && *RExC_parse != '\n') RExC_parse++;
            if (RExC_parse < RExC_end)
                goto tryagain;
        }
        /* FALL THROUGH */

    default: {
            register STRLEN len;
            register UV ender;
            register char *p;
            char *oldp, *s;
            STRLEN foldlen;
            U8 tmpbuf[UTF8_MAXBYTES_CASE+1], *foldbuf;

            parse_start = RExC_parse - 1;

            RExC_parse++;

        defchar:
            ender = 0;
            ret = reg_node(pRExC_state,
                           (U8)(FOLD ? (LOC ? EXACTFL : EXACTF) : EXACT));
            s = STRING(ret);
            for (len = 0, p = RExC_parse - 1;
              len < 127 && p < RExC_end;
              len++)
            {
                oldp = p;

                if (RExC_flags & PMf_EXTENDED)
                    p = regwhite(p, RExC_end);
                switch (*p) {
                case '^':
                case '$':
                case '.':
                case '[':
                case '(':
                case ')':
                case '|':
                    goto loopdone;
                case '\\':
                    switch (*++p) {
                    case 'A':
                    case 'C':
                    case 'X':
                    case 'G':
                    case 'Z':
                    case 'z':
                    case 'w':
                    case 'W':
                    case 'b':
                    case 'B':
                    case 's':
                    case 'S':
                    case 'd':
                    case 'D':
                    case 'p':
                    case 'P':
                        --p;
                        goto loopdone;
                    case 'n':
                        ender = '\n';
                        p++;
                        break;
                    case 'r':
                        ender = '\r';
                        p++;
                        break;
                    case 't':
                        ender = '\t';
                        p++;
                        break;
                    case 'f':
                        ender = '\f';
                        p++;
                        break;
                    case 'e':
                          ender = ASCII_TO_NATIVE('\033');
                        p++;
                        break;
                    case 'a':
                          ender = ASCII_TO_NATIVE('\007');
                        p++;
                        break;
                    case 'x':
                        if (*++p == '{') {
                            char* const e = strchr(p, '}');
        
                            if (!e) {
                                RExC_parse = p + 1;
                                vFAIL("Missing right brace on \\x{}");
                            }
                            else {
                                I32 flags = PERL_SCAN_ALLOW_UNDERSCORES
                                    | PERL_SCAN_DISALLOW_PREFIX;
                                STRLEN numlen = e - p - 1;
                                ender = grok_hex(p + 1, &numlen, &flags, NULL);
                                if (ender > 0xff)
                                    RExC_utf8 = 1;
                                p = e + 1;
                            }
                        }
                        else {
                            I32 flags = PERL_SCAN_DISALLOW_PREFIX;
                            STRLEN numlen = 2;
                            ender = grok_hex(p, &numlen, &flags, NULL);
                            p += numlen;
                        }
                        break;
                    case 'c':
                        p++;
                        ender = UCHARAT(p++);
                        ender = toCTRL(ender);
                        break;
                    case '0': case '1': case '2': case '3':case '4':
                    case '5': case '6': case '7': case '8':case '9':
                        if (*p == '0' ||
                          (isDIGIT(p[1]) && atoi(p) >= RExC_npar) ) {
                            I32 flags = 0;
                            STRLEN numlen = 3;
                            ender = grok_oct(p, &numlen, &flags, NULL);
                            p += numlen;
                        }
                        else {
                            --p;
                            goto loopdone;
                        }
                        break;
                    case '\0':
                        if (p >= RExC_end)
                            FAIL("Trailing \\");
                        /* FALL THROUGH */
                    default:
                        if (!SIZE_ONLY&& isALPHA(*p) && ckWARN(WARN_REGEXP))
                            vWARN2(p + 1, "Unrecognized escape \\%c passed through", UCHARAT(p));
                        goto normal_default;
                    }
                    break;
                default:
                  normal_default:
                    if (UTF8_IS_START(*p) && UTF) {
                        STRLEN numlen;
                        ender = utf8n_to_uvchr((U8*)p, RExC_end - p,
                                               &numlen, 0);
                        p += numlen;
                    }
                    else
                        ender = *p++;
                    break;
                }
                if (RExC_flags & PMf_EXTENDED)
                    p = regwhite(p, RExC_end);
                if (UTF && FOLD) {
                    /* Prime the casefolded buffer. */
                    ender = toFOLD_uni(ender, tmpbuf, &foldlen);
                }
                if (ISMULT2(p)) { /* Back off on ?+*. */
                    if (len)
                        p = oldp;
                    else if (UTF) {
                         if (FOLD) {
                              /* Emit all the Unicode characters. */
                              STRLEN numlen;
                              for (foldbuf = tmpbuf;
                                   foldlen;
                                   foldlen -= numlen) {
                                   ender = utf8_to_uvchr(foldbuf, &numlen);
                                   if (numlen > 0) {
                                        const STRLEN unilen = reguni(pRExC_state, ender, s);
                                        s       += unilen;
                                        len     += unilen;
                                        /* In EBCDIC the numlen
                                         * and unilen can differ. */
                                        foldbuf += numlen;
                                        if (numlen >= foldlen)
                                             break;
                                   }
                                   else
                                        break; /* "Can't happen." */
                              }
                         }
                         else {
                              const STRLEN unilen = reguni(pRExC_state, ender, s);
                              if (unilen > 0) {
                                   s   += unilen;
                                   len += unilen;
                              }
                         }
                    }
                    else {
                        len++;
                        REGC((char)ender, s++);
                    }
                    break;
                }
                if (UTF) {
                     if (FOLD) {
                          /* Emit all the Unicode characters. */
                          STRLEN numlen;
                          for (foldbuf = tmpbuf;
                               foldlen;
                               foldlen -= numlen) {
                               ender = utf8_to_uvchr(foldbuf, &numlen);
                               if (numlen > 0) {
                                    const STRLEN unilen = reguni(pRExC_state, ender, s);
                                    len     += unilen;
                                    s       += unilen;
                                    /* In EBCDIC the numlen
                                     * and unilen can differ. */
                                    foldbuf += numlen;
                                    if (numlen >= foldlen)
                                         break;
                               }
                               else
                                    break;
                          }
                     }
                     else {
                          const STRLEN unilen = reguni(pRExC_state, ender, s);
                          if (unilen > 0) {
                               s   += unilen;
                               len += unilen;
                          }
                     }
                     len--;
                }
                else
                    REGC((char)ender, s++);
            }
        loopdone:
            RExC_parse = p - 1;
            Set_Node_Cur_Length(ret); /* MJD */
            nextchar(pRExC_state);
            {
                /* len is STRLEN which is unsigned, need to copy to signed */
                IV iv = len;
                if (iv < 0)
                    vFAIL("Internal disaster");
            }
            if (len > 0)
                *flagp |= HASWIDTH;
            if (len == 1 && UNI_IS_INVARIANT(ender))
                *flagp |= SIMPLE;
            if (!SIZE_ONLY)
                STR_LEN(ret) = len;
            if (SIZE_ONLY)
                RExC_size += STR_SZ(len);
            else
                RExC_emit += STR_SZ(len);
        }
        break;
    }

    /* If the encoding pragma is in effect recode the text of
     * any EXACT-kind nodes. */
    if (PL_encoding && PL_regkind[(U8)OP(ret)] == EXACT) {
        STRLEN oldlen = STR_LEN(ret);
        SV *sv        = sv_2mortal(newSVpvn(STRING(ret), oldlen));

        if (RExC_utf8)
            SvUTF8_on(sv);
        if (sv_utf8_downgrade(sv, TRUE)) {
            const char * const s = sv_recode_to_utf8(sv, PL_encoding);
            const STRLEN newlen = SvCUR(sv);

            if (SvUTF8(sv))
                RExC_utf8 = 1;
            if (!SIZE_ONLY) {
                DEBUG_r(PerlIO_printf(Perl_debug_log, "recode %*s to %*s\n",
                                      (int)oldlen, STRING(ret),
                                      (int)newlen, s));
                Copy(s, STRING(ret), newlen, char);
                STR_LEN(ret) += newlen - oldlen;
                RExC_emit += STR_SZ(newlen) - STR_SZ(oldlen);
            } else
                RExC_size += STR_SZ(newlen) - STR_SZ(oldlen);
        }
    }

    return(ret);
}

STATIC char *
S_regwhite(char *p, const char *e)
{
    while (p < e) {
        if (isSPACE(*p))
            ++p;
        else if (*p == '#') {
            do {
                p++;
            } while (p < e && *p != '\n');
        }
        else
            break;
    }
    return p;
}

/* Parse POSIX character classes: [[:foo:]], [[=foo=]], [[.foo.]].
   Character classes ([:foo:]) can also be negated ([:^foo:]).
   Returns a named class id (ANYOF_XXX) if successful, -1 otherwise.
   Equivalence classes ([=foo=]) and composites ([.foo.]) are parsed,
   but trigger failures because they are currently unimplemented. */

#define POSIXCC_DONE(c)   ((c) == ':')
#define POSIXCC_NOTYET(c) ((c) == '=' || (c) == '.')
#define POSIXCC(c) (POSIXCC_DONE(c) || POSIXCC_NOTYET(c))

STATIC I32
S_regpposixcc(pTHX_ RExC_state_t *pRExC_state, I32 value)
{
    I32 namedclass = OOB_NAMEDCLASS;

    if (value == '[' && RExC_parse + 1 < RExC_end &&
        /* I smell either [: or [= or [. -- POSIX has been here, right? */
        POSIXCC(UCHARAT(RExC_parse))) {
        const char c = UCHARAT(RExC_parse);
        char* const s = RExC_parse++;
        
        while (RExC_parse < RExC_end && UCHARAT(RExC_parse) != c)
            RExC_parse++;
        if (RExC_parse == RExC_end)
            /* Grandfather lone [:, [=, [. */
            RExC_parse = s;
        else {
            const char* t = RExC_parse++; /* skip over the c */
            const char *posixcc;

            assert(*t == c);

            if (UCHARAT(RExC_parse) == ']') {
                RExC_parse++; /* skip over the ending ] */
                posixcc = s + 1;
                if (*s == ':') {
                    const I32 complement = *posixcc == '^' ? *posixcc++ : 0;
                    const I32 skip = t - posixcc;

                    /* Initially switch on the length of the name.  */
                    switch (skip) {
                    case 4:
                        if (memEQ(posixcc, "word", 4)) {
                            /* this is not POSIX, this is the Perl \w */;
                            namedclass
                                = complement ? ANYOF_NALNUM : ANYOF_ALNUM;
                        }
                        break;
                    case 5:
                        /* Names all of length 5.  */
                        /* alnum alpha ascii blank cntrl digit graph lower
                           print punct space upper  */
                        /* Offset 4 gives the best switch position.  */
                        switch (posixcc[4]) {
                        case 'a':
                            if (memEQ(posixcc, "alph", 4)) {
                                /*                  a     */
                                namedclass
                                    = complement ? ANYOF_NALPHA : ANYOF_ALPHA;
                            }
                            break;
                        case 'e':
                            if (memEQ(posixcc, "spac", 4)) {
                                /*                  e     */
                                namedclass
                                    = complement ? ANYOF_NPSXSPC : ANYOF_PSXSPC;
                            }
                            break;
                        case 'h':
                            if (memEQ(posixcc, "grap", 4)) {
                                /*                  h     */
                                namedclass
                                    = complement ? ANYOF_NGRAPH : ANYOF_GRAPH;
                            }
                            break;
                        case 'i':
                            if (memEQ(posixcc, "asci", 4)) {
                                /*                  i     */
                                namedclass
                                    = complement ? ANYOF_NASCII : ANYOF_ASCII;
                            }
                            break;
                        case 'k':
                            if (memEQ(posixcc, "blan", 4)) {
                                /*                  k     */
                                namedclass
                                    = complement ? ANYOF_NBLANK : ANYOF_BLANK;
                            }
                            break;
                        case 'l':
                            if (memEQ(posixcc, "cntr", 4)) {
                                /*                  l     */
                                namedclass
                                    = complement ? ANYOF_NCNTRL : ANYOF_CNTRL;
                            }
                            break;
                        case 'm':
                            if (memEQ(posixcc, "alnu", 4)) {
                                /*                  m     */
                                namedclass
                                    = complement ? ANYOF_NALNUMC : ANYOF_ALNUMC;
                            }
                            break;
                        case 'r':
                            if (memEQ(posixcc, "lowe", 4)) {
                                /*                  r     */
                                namedclass
                                    = complement ? ANYOF_NLOWER : ANYOF_LOWER;
                            }
                            if (memEQ(posixcc, "uppe", 4)) {
                                /*                  r     */
                                namedclass
                                    = complement ? ANYOF_NUPPER : ANYOF_UPPER;
                            }
                            break;
                        case 't':
                            if (memEQ(posixcc, "digi", 4)) {
                                /*                  t     */
                                namedclass
                                    = complement ? ANYOF_NDIGIT : ANYOF_DIGIT;
                            }
                            if (memEQ(posixcc, "prin", 4)) {
                                /*                  t     */
                                namedclass
                                    = complement ? ANYOF_NPRINT : ANYOF_PRINT;
                            }
                            if (memEQ(posixcc, "punc", 4)) {
                                /*                  t     */
                                namedclass
                                    = complement ? ANYOF_NPUNCT : ANYOF_PUNCT;
                            }
                            break;
                        }
                        break;
                    case 6:
                        if (memEQ(posixcc, "xdigit", 6)) {
                            namedclass
                                = complement ? ANYOF_NXDIGIT : ANYOF_XDIGIT;
                        }
                        break;
                    }

                    if (namedclass == OOB_NAMEDCLASS)
                    {
                        Simple_vFAIL3("POSIX class [:%.*s:] unknown",
                                      t - s - 1, s + 1);
                    }
                    assert (posixcc[skip] == ':');
                    assert (posixcc[skip+1] == ']');
                } else if (!SIZE_ONLY) {
                    /* [[=foo=]] and [[.foo.]] are still future. */

                    /* adjust RExC_parse so the warning shows after
                       the class closes */
                    while (UCHARAT(RExC_parse) && UCHARAT(RExC_parse) != ']')
                        RExC_parse++;
                    Simple_vFAIL3("POSIX syntax [%c %c] is reserved for future extensions", c, c);
                }
            } else {
                /* Maternal grandfather:
                 * "[:" ending in ":" but not in ":]" */
                RExC_parse = s;
            }
        }
    }

    return namedclass;
}

STATIC void
S_checkposixcc(pTHX_ RExC_state_t *pRExC_state)
{
    if (!SIZE_ONLY && POSIXCC(UCHARAT(RExC_parse))) {
        const char *s = RExC_parse;
        const char  c = *s++;

        while(*s && isALNUM(*s))
            s++;
        if (*s && c == *s && s[1] == ']') {
            if (ckWARN(WARN_REGEXP))
                vWARN3(s+2,
                        "POSIX syntax [%c %c] belongs inside character classes",
                        c, c);

            /* [[=foo=]] and [[.foo.]] are still future. */
            if (POSIXCC_NOTYET(c)) {
                /* adjust RExC_parse so the error shows after
                   the class closes */
                while (UCHARAT(RExC_parse) && UCHARAT(RExC_parse++) != ']')
                    ;
                Simple_vFAIL3("POSIX syntax [%c %c] is reserved for future extensions", c, c);
            }
        }
    }
}

STATIC regnode *
S_regclass(pTHX_ RExC_state_t *pRExC_state)
{
    register UV value = 0;
    register UV nextvalue;
    register IV prevvalue = OOB_UNICODE;
    register IV range = 0;
    register regnode *ret;
    STRLEN numlen;
    IV namedclass;
    char *rangebegin = NULL;
    bool need_class = 0;
    SV *listsv = NULL;
    register char *e;
    UV n;
    bool optimize_invert   = TRUE;
    AV* unicode_alternate  = NULL;
#ifdef EBCDIC
    UV literal_endpoint = 0;
#endif

    ret = reganode(pRExC_state, ANYOF, 0);

    if (!SIZE_ONLY)
        ANYOF_FLAGS(ret) = 0;

    if (UCHARAT(RExC_parse) == '^') {   /* Complement of range. */
        RExC_naughty++;
        RExC_parse++;
        if (!SIZE_ONLY)
            ANYOF_FLAGS(ret) |= ANYOF_INVERT;
    }

    if (SIZE_ONLY) {
        RExC_size += ANYOF_SKIP;
        listsv = &PL_sv_undef; /* For code scanners: listsv always non-NULL. */
    }
    else {
        RExC_emit += ANYOF_SKIP;
        if (FOLD)
            ANYOF_FLAGS(ret) |= ANYOF_FOLD;
        if (LOC)
            ANYOF_FLAGS(ret) |= ANYOF_LOCALE;
        ANYOF_BITMAP_ZERO(ret);
        listsv = newSVpvs("# comment\n");
    }

    nextvalue = RExC_parse < RExC_end ? UCHARAT(RExC_parse) : 0;

    if (!SIZE_ONLY && POSIXCC(nextvalue))
        checkposixcc(pRExC_state);

    /* allow 1st char to be ] (allowing it to be - is dealt with later) */
    if (UCHARAT(RExC_parse) == ']')
        goto charclassloop;

    while (RExC_parse < RExC_end && UCHARAT(RExC_parse) != ']') {

    charclassloop:

        namedclass = OOB_NAMEDCLASS; /* initialize as illegal */

        if (!range)
            rangebegin = RExC_parse;
        if (UTF) {
            value = utf8n_to_uvchr((U8*)RExC_parse,
                                   RExC_end - RExC_parse,
                                   &numlen, 0);
            RExC_parse += numlen;
        }
        else
            value = UCHARAT(RExC_parse++);
        nextvalue = RExC_parse < RExC_end ? UCHARAT(RExC_parse) : 0;
        if (value == '[' && POSIXCC(nextvalue))
            namedclass = regpposixcc(pRExC_state, value);
        else if (value == '\\') {
            if (UTF) {
                value = utf8n_to_uvchr((U8*)RExC_parse,
                                   RExC_end - RExC_parse,
                                   &numlen, 0);
                RExC_parse += numlen;
            }
            else
                value = UCHARAT(RExC_parse++);
            /* Some compilers cannot handle switching on 64-bit integer
             * values, therefore value cannot be an UV.  Yes, this will
             * be a problem later if we want switch on Unicode.
             * A similar issue a little bit later when switching on
             * namedclass. --jhi */
            switch ((I32)value) {
            case 'w':   namedclass = ANYOF_ALNUM;       break;
            case 'W':   namedclass = ANYOF_NALNUM;      break;
            case 's':   namedclass = ANYOF_SPACE;       break;
            case 'S':   namedclass = ANYOF_NSPACE;      break;
            case 'd':   namedclass = ANYOF_DIGIT;       break;
            case 'D':   namedclass = ANYOF_NDIGIT;      break;
            case 'p':
            case 'P':
                if (RExC_parse >= RExC_end)
                    vFAIL2("Empty \\%c{}", (U8)value);
                if (*RExC_parse == '{') {
                    const U8 c = (U8)value;
                    e = strchr(RExC_parse++, '}');
                    if (!e)
                        vFAIL2("Missing right brace on \\%c{}", c);
                    while (isSPACE(UCHARAT(RExC_parse)))
                        RExC_parse++;
                    if (e == RExC_parse)
                        vFAIL2("Empty \\%c{}", c);
                    n = e - RExC_parse;
                    while (isSPACE(UCHARAT(RExC_parse + n - 1)))
                        n--;
                }
                else {
                    e = RExC_parse;
                    n = 1;
                }
                if (!SIZE_ONLY) {
                    if (UCHARAT(RExC_parse) == '^') {
                         RExC_parse++;
                         n--;
                         value = value == 'p' ? 'P' : 'p'; /* toggle */
                         while (isSPACE(UCHARAT(RExC_parse))) {
                              RExC_parse++;
                              n--;
                         }
                    }
                    Perl_sv_catpvf(aTHX_ listsv, "%cutf8::%.*s\n",
                        (value=='p' ? '+' : '!'), (int)n, RExC_parse);
                }
                RExC_parse = e + 1;
                ANYOF_FLAGS(ret) |= ANYOF_UNICODE;
                namedclass = ANYOF_MAX;  /* no official name, but it's named */
                break;
            case 'n':   value = '\n';                   break;
            case 'r':   value = '\r';                   break;
            case 't':   value = '\t';                   break;
            case 'f':   value = '\f';                   break;
            case 'b':   value = '\b';                   break;
            case 'e':   value = ASCII_TO_NATIVE('\033');break;
            case 'a':   value = ASCII_TO_NATIVE('\007');break;
            case 'x':
                if (*RExC_parse == '{') {
                    I32 flags = PERL_SCAN_ALLOW_UNDERSCORES
                        | PERL_SCAN_DISALLOW_PREFIX;
                    e = strchr(RExC_parse++, '}');
                    if (!e)
                        vFAIL("Missing right brace on \\x{}");

                    numlen = e - RExC_parse;
                    value = grok_hex(RExC_parse, &numlen, &flags, NULL);
                    RExC_parse = e + 1;
                }
                else {
                    I32 flags = PERL_SCAN_DISALLOW_PREFIX;
                    numlen = 2;
                    value = grok_hex(RExC_parse, &numlen, &flags, NULL);
                    RExC_parse += numlen;
                }
                break;
            case 'c':
                value = UCHARAT(RExC_parse++);
                value = toCTRL(value);
                break;
            case '0': case '1': case '2': case '3': case '4':
            case '5': case '6': case '7': case '8': case '9':
            {
                I32 flags = 0;
                numlen = 3;
                value = grok_oct(--RExC_parse, &numlen, &flags, NULL);
                RExC_parse += numlen;
                break;
            }
            default:
                if (!SIZE_ONLY && isALPHA(value) && ckWARN(WARN_REGEXP))
                    vWARN2(RExC_parse,
                           "Unrecognized escape \\%c in character class passed through",
                           (int)value);
                break;
            }
        } /* end of \blah */
#ifdef EBCDIC
        else
            literal_endpoint++;
#endif

        if (namedclass > OOB_NAMEDCLASS) { /* this is a named class \blah */

            if (!SIZE_ONLY && !need_class)
                ANYOF_CLASS_ZERO(ret);

            need_class = 1;

            /* a bad range like a-\d, a-[:digit:] ? */
            if (range) {
                if (!SIZE_ONLY) {
                    if (ckWARN(WARN_REGEXP)) {
                        const int w =
                            RExC_parse >= rangebegin ?
                            RExC_parse - rangebegin : 0;
                        vWARN4(RExC_parse,
                               "False [] range \"%*.*s\"",
                               w, w, rangebegin);
                    }
                    if (prevvalue < 256) {
                        ANYOF_BITMAP_SET(ret, prevvalue);
                        ANYOF_BITMAP_SET(ret, '-');
                    }
                    else {
                        ANYOF_FLAGS(ret) |= ANYOF_UNICODE;
                        Perl_sv_catpvf(aTHX_ listsv,
                                       "%04"UVxf"\n%04"UVxf"\n", (UV)prevvalue, (UV) '-');
                    }
                }

                range = 0; /* this was not a true range */
            }

            if (!SIZE_ONLY) {
                const char *what = NULL;
                char yesno = 0;

                if (namedclass > OOB_NAMEDCLASS)
                    optimize_invert = FALSE;
                /* Possible truncation here but in some 64-bit environments
                 * the compiler gets heartburn about switch on 64-bit values.
                 * A similar issue a little earlier when switching on value.
                 * --jhi */
                switch ((I32)namedclass) {
                case ANYOF_ALNUM:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_ALNUM);
                    else {
                        for (value = 0; value < 256; value++)
                            if (isALNUM(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '+';
                    what = "Word";      
                    break;
                case ANYOF_NALNUM:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_NALNUM);
                    else {
                        for (value = 0; value < 256; value++)
                            if (!isALNUM(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '!';
                    what = "Word";
                    break;
                case ANYOF_ALNUMC:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_ALNUMC);
                    else {
                        for (value = 0; value < 256; value++)
                            if (isALNUMC(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '+';
                    what = "Alnum";
                    break;
                case ANYOF_NALNUMC:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_NALNUMC);
                    else {
                        for (value = 0; value < 256; value++)
                            if (!isALNUMC(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '!';
                    what = "Alnum";
                    break;
                case ANYOF_ALPHA:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_ALPHA);
                    else {
                        for (value = 0; value < 256; value++)
                            if (isALPHA(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '+';
                    what = "Alpha";
                    break;
                case ANYOF_NALPHA:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_NALPHA);
                    else {
                        for (value = 0; value < 256; value++)
                            if (!isALPHA(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '!';
                    what = "Alpha";
                    break;
                case ANYOF_ASCII:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_ASCII);
                    else {
#ifndef EBCDIC
                        for (value = 0; value < 128; value++)
                            ANYOF_BITMAP_SET(ret, value);
#else  /* EBCDIC */
                        for (value = 0; value < 256; value++) {
                            if (isASCII(value))
                                ANYOF_BITMAP_SET(ret, value);
                        }
#endif /* EBCDIC */
                    }
                    yesno = '+';
                    what = "ASCII";
                    break;
                case ANYOF_NASCII:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_NASCII);
                    else {
#ifndef EBCDIC
                        for (value = 128; value < 256; value++)
                            ANYOF_BITMAP_SET(ret, value);
#else  /* EBCDIC */
                        for (value = 0; value < 256; value++) {
                            if (!isASCII(value))
                                ANYOF_BITMAP_SET(ret, value);
                        }
#endif /* EBCDIC */
                    }
                    yesno = '!';
                    what = "ASCII";
                    break;
                case ANYOF_BLANK:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_BLANK);
                    else {
                        for (value = 0; value < 256; value++)
                            if (isBLANK(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '+';
                    what = "Blank";
                    break;
                case ANYOF_NBLANK:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_NBLANK);
                    else {
                        for (value = 0; value < 256; value++)
                            if (!isBLANK(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '!';
                    what = "Blank";
                    break;
                case ANYOF_CNTRL:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_CNTRL);
                    else {
                        for (value = 0; value < 256; value++)
                            if (isCNTRL(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '+';
                    what = "Cntrl";
                    break;
                case ANYOF_NCNTRL:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_NCNTRL);
                    else {
                        for (value = 0; value < 256; value++)
                            if (!isCNTRL(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '!';
                    what = "Cntrl";
                    break;
                case ANYOF_DIGIT:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_DIGIT);
                    else {
                        /* consecutive digits assumed */
                        for (value = '0'; value <= '9'; value++)
                            ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '+';
                    what = "Digit";
                    break;
                case ANYOF_NDIGIT:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_NDIGIT);
                    else {
                        /* consecutive digits assumed */
                        for (value = 0; value < '0'; value++)
                            ANYOF_BITMAP_SET(ret, value);
                        for (value = '9' + 1; value < 256; value++)
                            ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '!';
                    what = "Digit";
                    break;
                case ANYOF_GRAPH:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_GRAPH);
                    else {
                        for (value = 0; value < 256; value++)
                            if (isGRAPH(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '+';
                    what = "Graph";
                    break;
                case ANYOF_NGRAPH:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_NGRAPH);
                    else {
                        for (value = 0; value < 256; value++)
                            if (!isGRAPH(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '!';
                    what = "Graph";
                    break;
                case ANYOF_LOWER:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_LOWER);
                    else {
                        for (value = 0; value < 256; value++)
                            if (isLOWER(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '+';
                    what = "Lower";
                    break;
                case ANYOF_NLOWER:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_NLOWER);
                    else {
                        for (value = 0; value < 256; value++)
                            if (!isLOWER(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '!';
                    what = "Lower";
                    break;
                case ANYOF_PRINT:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_PRINT);
                    else {
                        for (value = 0; value < 256; value++)
                            if (isPRINT(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '+';
                    what = "Print";
                    break;
                case ANYOF_NPRINT:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_NPRINT);
                    else {
                        for (value = 0; value < 256; value++)
                            if (!isPRINT(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '!';
                    what = "Print";
                    break;
                case ANYOF_PSXSPC:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_PSXSPC);
                    else {
                        for (value = 0; value < 256; value++)
                            if (isPSXSPC(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '+';
                    what = "Space";
                    break;
                case ANYOF_NPSXSPC:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_NPSXSPC);
                    else {
                        for (value = 0; value < 256; value++)
                            if (!isPSXSPC(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '!';
                    what = "Space";
                    break;
                case ANYOF_PUNCT:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_PUNCT);
                    else {
                        for (value = 0; value < 256; value++)
                            if (isPUNCT(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '+';
                    what = "Punct";
                    break;
                case ANYOF_NPUNCT:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_NPUNCT);
                    else {
                        for (value = 0; value < 256; value++)
                            if (!isPUNCT(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '!';
                    what = "Punct";
                    break;
                case ANYOF_SPACE:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_SPACE);
                    else {
                        for (value = 0; value < 256; value++)
                            if (isSPACE(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '+';
                    what = "SpacePerl";
                    break;
                case ANYOF_NSPACE:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_NSPACE);
                    else {
                        for (value = 0; value < 256; value++)
                            if (!isSPACE(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '!';
                    what = "SpacePerl";
                    break;
                case ANYOF_UPPER:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_UPPER);
                    else {
                        for (value = 0; value < 256; value++)
                            if (isUPPER(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '+';
                    what = "Upper";
                    break;
                case ANYOF_NUPPER:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_NUPPER);
                    else {
                        for (value = 0; value < 256; value++)
                            if (!isUPPER(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '!';
                    what = "Upper";
                    break;
                case ANYOF_XDIGIT:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_XDIGIT);
                    else {
                        for (value = 0; value < 256; value++)
                            if (isXDIGIT(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '+';
                    what = "XDigit";
                    break;
                case ANYOF_NXDIGIT:
                    if (LOC)
                        ANYOF_CLASS_SET(ret, ANYOF_NXDIGIT);
                    else {
                        for (value = 0; value < 256; value++)
                            if (!isXDIGIT(value))
                                ANYOF_BITMAP_SET(ret, value);
                    }
                    yesno = '!';
                    what = "XDigit";
                    break;
                case ANYOF_MAX:
                    /* this is to handle \p and \P */
                    break;
                default:
                    vFAIL("Invalid [::] class");
                    break;
                }
                if (what) {
                    /* Strings such as "+utf8::isWord\n" */
                    Perl_sv_catpvf(aTHX_ listsv, "%cutf8::Is%s\n", yesno, what);
                }
                if (LOC)
                    ANYOF_FLAGS(ret) |= ANYOF_CLASS;
                continue;
            }
        } /* end of namedclass \blah */

        if (range) {
            if (prevvalue > (IV)value) /* b-a */ {
                const int w = RExC_parse - rangebegin;
                Simple_vFAIL4("Invalid [] range \"%*.*s\"", w, w, rangebegin);
                range = 0; /* not a valid range */
            }
        }
        else {
            prevvalue = value; /* save the beginning of the range */
            if (*RExC_parse == '-' && RExC_parse+1 < RExC_end &&
                RExC_parse[1] != ']') {
                RExC_parse++;

                /* a bad range like \w-, [:word:]- ? */
                if (namedclass > OOB_NAMEDCLASS) {
                    if (ckWARN(WARN_REGEXP)) {
                        const int w =
                            RExC_parse >= rangebegin ?
                            RExC_parse - rangebegin : 0;
                        vWARN4(RExC_parse,
                               "False [] range \"%*.*s\"",
                               w, w, rangebegin);
                    }
                    if (!SIZE_ONLY)
                        ANYOF_BITMAP_SET(ret, '-');
                } else
                    range = 1;  /* yeah, it's a range! */
                continue;       /* but do it the next time */
            }
        }

        /* now is the next time */
        if (!SIZE_ONLY) {
            IV i;

            if (prevvalue < 256) {
                const IV ceilvalue = value < 256 ? value : 255;

#ifdef EBCDIC
                /* In EBCDIC [\x89-\x91] should include
                 * the \x8e but [i-j] should not. */
                if (literal_endpoint == 2 &&
                    ((isLOWER(prevvalue) && isLOWER(ceilvalue)) ||
                     (isUPPER(prevvalue) && isUPPER(ceilvalue))))
                {
                    if (isLOWER(prevvalue)) {
                        for (i = prevvalue; i <= ceilvalue; i++)
                            if (isLOWER(i))
                                ANYOF_BITMAP_SET(ret, i);
                    } else {
                        for (i = prevvalue; i <= ceilvalue; i++)
                            if (isUPPER(i))
                                ANYOF_BITMAP_SET(ret, i);
                    }
                }
                else
#endif
                      for (i = prevvalue; i <= ceilvalue; i++)
                          ANYOF_BITMAP_SET(ret, i);
          }
          if (value > 255 || UTF) {
                const UV prevnatvalue  = NATIVE_TO_UNI(prevvalue);
                const UV natvalue      = NATIVE_TO_UNI(value);

                ANYOF_FLAGS(ret) |= ANYOF_UNICODE;
                if (prevnatvalue < natvalue) { /* what about > ? */
                    Perl_sv_catpvf(aTHX_ listsv, "%04"UVxf"\t%04"UVxf"\n",
                                   prevnatvalue, natvalue);
                }
                else if (prevnatvalue == natvalue) {
                    Perl_sv_catpvf(aTHX_ listsv, "%04"UVxf"\n", natvalue);
                    if (FOLD) {
                         U8 foldbuf[UTF8_MAXBYTES_CASE+1];
                         STRLEN foldlen;
                         const UV f = to_uni_fold(natvalue, foldbuf, &foldlen);

#ifdef EBCDIC /* RD t/uni/fold ff and 6b */
                         if (RExC_precomp[0] == ':' &&
                             RExC_precomp[1] == '[' &&
                             (f == 0xDF || f == 0x92)) {
                             f = NATIVE_TO_UNI(f);
                        }
#endif
                         /* If folding and foldable and a single
                          * character, insert also the folded version
                          * to the charclass. */
                         if (f != value) {
#ifdef EBCDIC /* RD tunifold ligatures s,t fb05, fb06 */
                             if ((RExC_precomp[0] == ':' &&
                                  RExC_precomp[1] == '[' &&
                                  (f == 0xA2 &&
                                   (value == 0xFB05 || value == 0xFB06))) ?
                                 foldlen == ((STRLEN)UNISKIP(f) - 1) :
                                 foldlen == (STRLEN)UNISKIP(f) )
#else
                              if (foldlen == (STRLEN)UNISKIP(f))
#endif
                                  Perl_sv_catpvf(aTHX_ listsv,
                                                 "%04"UVxf"\n", f);
                              else {
                                  /* Any multicharacter foldings
                                   * require the following transform:
                                   * [ABCDEF] -> (?:[ABCabcDEFd]|pq|rst)
                                   * where E folds into "pq" and F folds
                                   * into "rst", all other characters
                                   * fold to single characters.  We save
                                   * away these multicharacter foldings,
                                   * to be later saved as part of the
                                   * additional "s" data. */
                                  SV *sv;

                                  if (!unicode_alternate)
                                      unicode_alternate = newAV();
                                  sv = newSVpvn((char*)foldbuf, foldlen);
                                  SvUTF8_on(sv);
                                  av_push(unicode_alternate, sv);
                              }
                         }

                         /* If folding and the value is one of the Greek
                          * sigmas insert a few more sigmas to make the
                          * folding rules of the sigmas to work right.
                          * Note that not all the possible combinations
                          * are handled here: some of them are handled
                          * by the standard folding rules, and some of
                          * them (literal or EXACTF cases) are handled
                          * during runtime in regexec.c:S_find_byclass(). */
                         if (value == UNICODE_GREEK_SMALL_LETTER_FINAL_SIGMA) {
                              Perl_sv_catpvf(aTHX_ listsv, "%04"UVxf"\n",
                                             (UV)UNICODE_GREEK_CAPITAL_LETTER_SIGMA);
                              Perl_sv_catpvf(aTHX_ listsv, "%04"UVxf"\n",
                                             (UV)UNICODE_GREEK_SMALL_LETTER_SIGMA);
                         }
                         else if (value == UNICODE_GREEK_CAPITAL_LETTER_SIGMA)
                              Perl_sv_catpvf(aTHX_ listsv, "%04"UVxf"\n",
                                             (UV)UNICODE_GREEK_SMALL_LETTER_SIGMA);
                    }
                }
            }
#ifdef EBCDIC
            literal_endpoint = 0;
#endif
        }

        range = 0; /* this range (if it was one) is done now */
    }

    if (need_class) {
        ANYOF_FLAGS(ret) |= ANYOF_LARGE;
        if (SIZE_ONLY)
            RExC_size += ANYOF_CLASS_ADD_SKIP;
        else
            RExC_emit += ANYOF_CLASS_ADD_SKIP;
    }

    /* optimize case-insensitive simple patterns (e.g. /[a-z]/i) */
    if (!SIZE_ONLY &&
         /* If the only flag is folding (plus possibly inversion). */
        ((ANYOF_FLAGS(ret) & (ANYOF_FLAGS_ALL ^ ANYOF_INVERT)) == ANYOF_FOLD)
       ) {
        for (value = 0; value < 256; ++value) {
            if (ANYOF_BITMAP_TEST(ret, value)) {
                UV fold = PL_fold[value];

                if (fold != value)
                    ANYOF_BITMAP_SET(ret, fold);
            }
        }
        ANYOF_FLAGS(ret) &= ~ANYOF_FOLD;
    }

    /* optimize inverted simple patterns (e.g. [^a-z]) */
    if (!SIZE_ONLY && optimize_invert &&
        /* If the only flag is inversion. */
        (ANYOF_FLAGS(ret) & ANYOF_FLAGS_ALL) == ANYOF_INVERT) {
        for (value = 0; value < ANYOF_BITMAP_SIZE; ++value)
            ANYOF_BITMAP(ret)[value] ^= ANYOF_FLAGS_ALL;
        ANYOF_FLAGS(ret) = ANYOF_UNICODE_ALL;
    }

    if (!SIZE_ONLY) {
        AV * const av = newAV();
        SV *rv;

        /* The 0th element stores the character class description
         * in its textual form: used later (regexec.c:Perl_regclass_swash())
         * to initialize the appropriate swash (which gets stored in
         * the 1st element), and also useful for dumping the regnode.
         * The 2nd element stores the multicharacter foldings,
         * used later (regexec.c:S_reginclass()). */
        av_store(av, 0, listsv);
        av_store(av, 1, NULL);
        av_store(av, 2, (SV*)unicode_alternate);
        rv = newRV_noinc((SV*)av);
        n = add_data(pRExC_state, 1, "s");
        RExC_rx->data->data[n] = (void*)rv;
        ARG_SET(ret, n);
    }

    return ret;
}

STATIC char*
S_nextchar(pTHX_ RExC_state_t *pRExC_state)
{
    char* const retval = RExC_parse++;

    for (;;) {
        if (*RExC_parse == '(' && RExC_parse[1] == '?' &&
                RExC_parse[2] == '#') {
            while (*RExC_parse != ')') {
                if (RExC_parse == RExC_end)
                    FAIL("Sequence (?#... not terminated");
                RExC_parse++;
            }
            RExC_parse++;
            continue;
        }
        if (RExC_flags & PMf_EXTENDED) {
            if (isSPACE(*RExC_parse)) {
                RExC_parse++;
                continue;
            }
            else if (*RExC_parse == '#') {
                while (RExC_parse < RExC_end)
                    if (*RExC_parse++ == '\n') break;
                continue;
            }
        }
        return retval;
    }
}

/*
- reg_node - emit a node
*/
STATIC regnode *                        /* Location. */
S_reg_node(pTHX_ RExC_state_t *pRExC_state, U8 op)
{
    register regnode *ptr;
    regnode * const ret = RExC_emit;

    if (SIZE_ONLY) {
        SIZE_ALIGN(RExC_size);
        RExC_size += 1;
        return(ret);
    }

    NODE_ALIGN_FILL(ret);
    ptr = ret;
    FILL_ADVANCE_NODE(ptr, op);
    if (RExC_offsets) {         /* MJD */
        MJD_OFFSET_DEBUG(("%s:%u: (op %s) %s %u <- %u (len %u) (max %u).\n", 
              "reg_node", __LINE__, 
              reg_name[op],
              RExC_emit - RExC_emit_start > RExC_offsets[0] 
              ? "Overwriting end of array!\n" : "OK",
              RExC_emit - RExC_emit_start,
              RExC_parse - RExC_start,
              RExC_offsets[0])); 
        Set_Node_Offset(RExC_emit, RExC_parse + (op == END));
    }
            
    RExC_emit = ptr;

    return(ret);
}

/*
- reganode - emit a node with an argument
*/
STATIC regnode *                        /* Location. */
S_reganode(pTHX_ RExC_state_t *pRExC_state, U8 op, U32 arg)
{
    register regnode *ptr;
    regnode * const ret = RExC_emit;

    if (SIZE_ONLY) {
        SIZE_ALIGN(RExC_size);
        RExC_size += 2;
        return(ret);
    }

    NODE_ALIGN_FILL(ret);
    ptr = ret;
    FILL_ADVANCE_NODE_ARG(ptr, op, arg);
    if (RExC_offsets) {         /* MJD */
        MJD_OFFSET_DEBUG(("%s(%d): (op %s) %s %u <- %u (max %u).\n", 
              "reganode",
              __LINE__,
              reg_name[op],
              RExC_emit - RExC_emit_start > RExC_offsets[0] ? 
              "Overwriting end of array!\n" : "OK",
              RExC_emit - RExC_emit_start,
              RExC_parse - RExC_start,
              RExC_offsets[0])); 
        Set_Cur_Node_Offset;
    }
            
    RExC_emit = ptr;

    return(ret);
}

/*
- reguni - emit (if appropriate) a Unicode character
*/
STATIC STRLEN
S_reguni(pTHX_ const RExC_state_t *pRExC_state, UV uv, char* s)
{
    return SIZE_ONLY ? UNISKIP(uv) : (uvchr_to_utf8((U8*)s, uv) - (U8*)s);
}

/*
- reginsert - insert an operator in front of already-emitted operand
*
* Means relocating the operand.
*/
STATIC void
S_reginsert(pTHX_ RExC_state_t *pRExC_state, U8 op, regnode *opnd)
{
    register regnode *src;
    register regnode *dst;
    register regnode *place;
    const int offset = regarglen[(U8)op];

/* (PL_regkind[(U8)op] == CURLY ? EXTRA_STEP_2ARGS : 0); */

    if (SIZE_ONLY) {
        RExC_size += NODE_STEP_REGNODE + offset;
        return;
    }

    src = RExC_emit;
    RExC_emit += NODE_STEP_REGNODE + offset;
    dst = RExC_emit;
    while (src > opnd) {
        StructCopy(--src, --dst, regnode);
        if (RExC_offsets) {     /* MJD 20010112 */
            MJD_OFFSET_DEBUG(("%s(%d): (op %s) %s copy %u -> %u (max %u).\n",
                  "reg_insert",
                  __LINE__,
                  reg_name[op],
                  dst - RExC_emit_start > RExC_offsets[0] 
                  ? "Overwriting end of array!\n" : "OK",
                  src - RExC_emit_start,
                  dst - RExC_emit_start,
                  RExC_offsets[0])); 
            Set_Node_Offset_To_R(dst-RExC_emit_start, Node_Offset(src));
            Set_Node_Length_To_R(dst-RExC_emit_start, Node_Length(src));
        }
    }
    

    place = opnd;               /* Op node, where operand used to be. */
    if (RExC_offsets) {         /* MJD */
        MJD_OFFSET_DEBUG(("%s(%d): (op %s) %s %u <- %u (max %u).\n", 
              "reginsert",
              __LINE__,
              reg_name[op],
              place - RExC_emit_start > RExC_offsets[0] 
              ? "Overwriting end of array!\n" : "OK",
              place - RExC_emit_start,
              RExC_parse - RExC_start,
              RExC_offsets[0])); 
        Set_Node_Offset(place, RExC_parse);
        Set_Node_Length(place, 1);
    }
    src = NEXTOPER(place);
    FILL_ADVANCE_NODE(place, op);
    Zero(src, offset, regnode);
}

/*
- regtail - set the next-pointer at the end of a node chain of p to val.
*/
/* TODO: All three parms should be const */
STATIC void
S_regtail(pTHX_ const RExC_state_t *pRExC_state, regnode *p, const regnode *val)
{
    register regnode *scan;

    if (SIZE_ONLY)
        return;

    /* Find last node. */
    scan = p;
    for (;;) {
        regnode * const temp = regnext(scan);
        if (temp == NULL)
            break;
        scan = temp;
    }

    if (reg_off_by_arg[OP(scan)]) {
        ARG_SET(scan, val - scan);
    }
    else {
        NEXT_OFF(scan) = val - scan;
    }
}

/*
 - regcurly - a little FSA that accepts {\d+,?\d*}
 */
STATIC I32
S_regcurly(register const char *s)
{
    if (*s++ != '{')
        return FALSE;
    if (!isDIGIT(*s))
        return FALSE;
    while (isDIGIT(*s))
        s++;
    if (*s == ',')
        s++;
    while (isDIGIT(*s))
        s++;
    if (*s != '}')
        return FALSE;
    return TRUE;
}

/*
 - regdump - dump a regexp onto Perl_debug_log in vaguely comprehensible form
 */
void
Perl_regdump(pTHX_ const regexp *r)
{
#ifdef DEBUGGING
    SV * const sv = sv_newmortal();

    (void)dumpuntil(r->program, r->program + 1, NULL, sv, 0);

    /* Header fields of interest. */
    if (r->anchored_substr)
        PerlIO_printf(Perl_debug_log,
                      "anchored \"%s%.*s%s\"%s at %"IVdf" ",
                      PL_colors[0],
                      (int)(SvCUR(r->anchored_substr) - (SvTAIL(r->anchored_substr)!=0)),
                      SvPVX_const(r->anchored_substr),
                      PL_colors[1],
                      SvTAIL(r->anchored_substr) ? "$" : "",
                      (IV)r->anchored_offset);
    else if (r->anchored_utf8)
        PerlIO_printf(Perl_debug_log,
                      "anchored utf8 \"%s%.*s%s\"%s at %"IVdf" ",
                      PL_colors[0],
                      (int)(SvCUR(r->anchored_utf8) - (SvTAIL(r->anchored_utf8)!=0)),
                      SvPVX_const(r->anchored_utf8),
                      PL_colors[1],
                      SvTAIL(r->anchored_utf8) ? "$" : "",
                      (IV)r->anchored_offset);
    if (r->float_substr)
        PerlIO_printf(Perl_debug_log,
                      "floating \"%s%.*s%s\"%s at %"IVdf"..%"UVuf" ",
                      PL_colors[0],
                      (int)(SvCUR(r->float_substr) - (SvTAIL(r->float_substr)!=0)),
                      SvPVX_const(r->float_substr),
                      PL_colors[1],
                      SvTAIL(r->float_substr) ? "$" : "",
                      (IV)r->float_min_offset, (UV)r->float_max_offset);
    else if (r->float_utf8)
        PerlIO_printf(Perl_debug_log,
                      "floating utf8 \"%s%.*s%s\"%s at %"IVdf"..%"UVuf" ",
                      PL_colors[0],
                      (int)(SvCUR(r->float_utf8) - (SvTAIL(r->float_utf8)!=0)),
                      SvPVX_const(r->float_utf8),
                      PL_colors[1],
                      SvTAIL(r->float_utf8) ? "$" : "",
                      (IV)r->float_min_offset, (UV)r->float_max_offset);
    if (r->check_substr || r->check_utf8)
        PerlIO_printf(Perl_debug_log,
                      (const char *)
                      (r->check_substr == r->float_substr
                       && r->check_utf8 == r->float_utf8
                       ? "(checking floating" : "(checking anchored"));
    if (r->reganch & ROPT_NOSCAN)
        PerlIO_printf(Perl_debug_log, " noscan");
    if (r->reganch & ROPT_CHECK_ALL)
        PerlIO_printf(Perl_debug_log, " isall");
    if (r->check_substr || r->check_utf8)
        PerlIO_printf(Perl_debug_log, ") ");

    if (r->regstclass) {
        regprop(sv, r->regstclass);
        PerlIO_printf(Perl_debug_log, "stclass \"%s\" ", SvPVX_const(sv));
    }
    if (r->reganch & ROPT_ANCH) {
        PerlIO_printf(Perl_debug_log, "anchored");
        if (r->reganch & ROPT_ANCH_BOL)
            PerlIO_printf(Perl_debug_log, "(BOL)");
        if (r->reganch & ROPT_ANCH_MBOL)
            PerlIO_printf(Perl_debug_log, "(MBOL)");
        if (r->reganch & ROPT_ANCH_SBOL)
            PerlIO_printf(Perl_debug_log, "(SBOL)");
        if (r->reganch & ROPT_ANCH_GPOS)
            PerlIO_printf(Perl_debug_log, "(GPOS)");
        PerlIO_putc(Perl_debug_log, ' ');
    }
    if (r->reganch & ROPT_GPOS_SEEN)
        PerlIO_printf(Perl_debug_log, "GPOS ");
    if (r->reganch & ROPT_SKIP)
        PerlIO_printf(Perl_debug_log, "plus ");
    if (r->reganch & ROPT_IMPLICIT)
        PerlIO_printf(Perl_debug_log, "implicit ");
    PerlIO_printf(Perl_debug_log, "minlen %ld ", (long) r->minlen);
    if (r->reganch & ROPT_EVAL_SEEN)
        PerlIO_printf(Perl_debug_log, "with eval ");
    PerlIO_printf(Perl_debug_log, "\n");
    if (r->offsets) {
      U32 i;
      const U32 len = r->offsets[0];
      PerlIO_printf(Perl_debug_log, "Offsets: [%"UVuf"]\n\t", (UV)r->offsets[0]);
      for (i = 1; i <= len; i++)
        PerlIO_printf(Perl_debug_log, "%"UVuf"[%"UVuf"] ", 
                      (UV)r->offsets[i*2-1], 
                      (UV)r->offsets[i*2]);
      PerlIO_printf(Perl_debug_log, "\n");
    }
#else
    PERL_UNUSED_CONTEXT;
    PERL_UNUSED_ARG(r);
#endif  /* DEBUGGING */
}

/*
- regprop - printable representation of opcode
*/
void
Perl_regprop(pTHX_ SV *sv, regnode *o)
{
#ifdef DEBUGGING
    register int k;

    sv_setpvn(sv, "", 0);
    if (OP(o) >= reg_num)               /* regnode.type is unsigned */
        /* It would be nice to FAIL() here, but this may be called from
           regexec.c, and it would be hard to supply pRExC_state. */
        Perl_croak(aTHX_ "Corrupted regexp opcode");
    sv_catpv(sv, reg_name[OP(o)]); /* Take off const! */

    k = PL_regkind[(U8)OP(o)];

    if (k == EXACT) {
        SV * const dsv = sv_2mortal(newSVpvs(""));
        /* Using is_utf8_string() is a crude hack but it may
         * be the best for now since we have no flag "this EXACTish
         * node was UTF-8" --jhi */
        const bool do_utf8 = is_utf8_string((U8*)STRING(o), STR_LEN(o));
        const char * const s = do_utf8 ?
          pv_uni_display(dsv, (U8*)STRING(o), STR_LEN(o), 60,
                         UNI_DISPLAY_REGEX) :
          STRING(o);
        const int len = do_utf8 ?
          strlen(s) :
          STR_LEN(o);
        Perl_sv_catpvf(aTHX_ sv, " <%s%.*s%s>",
                       PL_colors[0],
                       len, s,
                       PL_colors[1]);
    }
    else if (k == CURLY) {
        if (OP(o) == CURLYM || OP(o) == CURLYN || OP(o) == CURLYX)
            Perl_sv_catpvf(aTHX_ sv, "[%d]", o->flags); /* Parenth number */
        Perl_sv_catpvf(aTHX_ sv, " {%d,%d}", ARG1(o), ARG2(o));
    }
    else if (k == WHILEM && o->flags)                   /* Ordinal/of */
        Perl_sv_catpvf(aTHX_ sv, "[%d/%d]", o->flags & 0xf, o->flags>>4);
    else if (k == REF || k == OPEN || k == CLOSE || k == GROUPP )
        Perl_sv_catpvf(aTHX_ sv, "%d", (int)ARG(o));    /* Parenth number */
    else if (k == LOGICAL)
        Perl_sv_catpvf(aTHX_ sv, "[%d]", o->flags);     /* 2: embedded, otherwise 1 */
    else if (k == ANYOF) {
        int i, rangestart = -1;
        const U8 flags = ANYOF_FLAGS(o);

        /* Should be synchronized with * ANYOF_ #xdefines in regcomp.h */
        static const char * const anyofs[] = {
            "\\w",
            "\\W",
            "\\s",
            "\\S",
            "\\d",
            "\\D",
            "[:alnum:]",
            "[:^alnum:]",
            "[:alpha:]",
            "[:^alpha:]",
            "[:ascii:]",
            "[:^ascii:]",
            "[:ctrl:]",
            "[:^ctrl:]",
            "[:graph:]",
            "[:^graph:]",
            "[:lower:]",
            "[:^lower:]",
            "[:print:]",
            "[:^print:]",
            "[:punct:]",
            "[:^punct:]",
            "[:upper:]",
            "[:^upper:]",
            "[:xdigit:]",
            "[:^xdigit:]",
            "[:space:]",
            "[:^space:]",
            "[:blank:]",
            "[:^blank:]"
        };

        if (flags & ANYOF_LOCALE)
            sv_catpvs(sv, "{loc}");
        if (flags & ANYOF_FOLD)
            sv_catpvs(sv, "{i}");
        Perl_sv_catpvf(aTHX_ sv, "[%s", PL_colors[0]);
        if (flags & ANYOF_INVERT)
            sv_catpvs(sv, "^");
        for (i = 0; i <= 256; i++) {
            if (i < 256 && ANYOF_BITMAP_TEST(o,i)) {
                if (rangestart == -1)
                    rangestart = i;
            } else if (rangestart != -1) {
                if (i <= rangestart + 3)
                    for (; rangestart < i; rangestart++)
                        put_byte(sv, rangestart);
                else {
                    put_byte(sv, rangestart);
                    sv_catpvs(sv, "-");
                    put_byte(sv, i - 1);
                }
                rangestart = -1;
            }
        }

        if (o->flags & ANYOF_CLASS)
            for (i = 0; i < (int)(sizeof(anyofs)/sizeof(char*)); i++)
                if (ANYOF_CLASS_TEST(o,i))
                    sv_catpv(sv, anyofs[i]);

        if (flags & ANYOF_UNICODE)
            sv_catpvs(sv, "{unicode}");
        else if (flags & ANYOF_UNICODE_ALL)
            sv_catpvs(sv, "{unicode_all}");

        {
            SV *lv;
            SV * const sw = regclass_swash(o, FALSE, &lv, 0);
        
            if (lv) {
                if (sw) {
                    U8 s[UTF8_MAXBYTES_CASE+1];
                
                    for (i = 0; i <= 256; i++) { /* just the first 256 */
                        uvchr_to_utf8(s, i);
                        
                        if (i < 256 && swash_fetch(sw, s, TRUE)) {
                            if (rangestart == -1)
                                rangestart = i;
                        } else if (rangestart != -1) {
                            if (i <= rangestart + 3)
                                for (; rangestart < i; rangestart++) {
                                    const U8 * const e = uvchr_to_utf8(s,rangestart);
                                    U8 *p;
                                    for(p = s; p < e; p++)
                                        put_byte(sv, *p);
                                }
                            else {
                                const U8 *e = uvchr_to_utf8(s,rangestart);
                                U8 *p;
                                for (p = s; p < e; p++)
                                    put_byte(sv, *p);
                                sv_catpvs(sv, "-");
                                e = uvchr_to_utf8(s, i-1);
                                for (p = s; p < e; p++)
                                    put_byte(sv, *p);
                                }
                                rangestart = -1;
                            }
                        }
                        
                    sv_catpvs(sv, "..."); /* et cetera */
                }

                {
                    char *s = savesvpv(lv);
                    char * const origs = s;
                
                    while(*s && *s != '\n') s++;
                
                    if (*s == '\n') {
                        const char * const t = ++s;
                        
                        while (*s) {
                            if (*s == '\n')
                                *s = ' ';
                            s++;
                        }
                        if (s[-1] == ' ')
                            s[-1] = 0;
                        
                        sv_catpv(sv, t);
                    }
                
                    Safefree(origs);
                }
            }
        }

        Perl_sv_catpvf(aTHX_ sv, "%s]", PL_colors[1]);
    }
    else if (k == BRANCHJ && (OP(o) == UNLESSM || OP(o) == IFMATCH))
        Perl_sv_catpvf(aTHX_ sv, "[-%d]", o->flags);
#else
    PERL_UNUSED_CONTEXT;
    PERL_UNUSED_ARG(sv);
    PERL_UNUSED_ARG(o);
#endif  /* DEBUGGING */
}

SV *
Perl_re_intuit_string(pTHX_ regexp *prog)
{                               /* Assume that RE_INTUIT is set */
    DEBUG_r(
        {
            const char * const s = SvPV_nolen_const(prog->check_substr
                      ? prog->check_substr : prog->check_utf8);

            if (!PL_colorset) reginitcolors();
            PerlIO_printf(Perl_debug_log,
                      "%sUsing REx %ssubstr:%s \"%s%.60s%s%s\"\n",
                      PL_colors[4],
                      prog->check_substr ? "" : "utf8 ",
                      PL_colors[5],PL_colors[0],
                      s,
                      PL_colors[1],
                      (strlen(s) > 60 ? "..." : ""));
        } );

    return prog->check_substr ? prog->check_substr : prog->check_utf8;
}

void
Perl_pregfree(pTHX_ struct regexp *r)
{
#ifdef DEBUGGING
    SV * const dsv = PERL_DEBUG_PAD_ZERO(0);
#endif

    if (!r || (--r->refcnt > 0))
        return;
    DEBUG_r({
        const char * const s = (r->reganch & ROPT_UTF8)
            ? pv_uni_display(dsv, (U8*)r->precomp, r->prelen, 60, UNI_DISPLAY_REGEX)
            : pv_display(dsv, r->precomp, r->prelen, 0, 60);
        const int len = SvCUR(dsv);
         if (!PL_colorset)
              reginitcolors();
         PerlIO_printf(Perl_debug_log,
                       "%sFreeing REx:%s `%s%*.*s%s%s'\n",
                       PL_colors[4],PL_colors[5],PL_colors[0],
                       len, len, s,
                       PL_colors[1],
                       len > 60 ? "..." : "");
    });

    /* gcov results gave these as non-null 100% of the time, so there's no
       optimisation in checking them before calling Safefree  */
    Safefree(r->precomp);
    Safefree(r->offsets);             /* 20010421 MJD */
    if (RX_MATCH_COPIED(r))
        Safefree(r->subbeg);
    if (r->substrs) {
        if (r->anchored_substr)
            SvREFCNT_dec(r->anchored_substr);
        if (r->anchored_utf8)
            SvREFCNT_dec(r->anchored_utf8);
        if (r->float_substr)
            SvREFCNT_dec(r->float_substr);
        if (r->float_utf8)
            SvREFCNT_dec(r->float_utf8);
        Safefree(r->substrs);
    }
    if (r->data) {
        int n = r->data->count;
        PAD* new_comppad = NULL;
        PAD* old_comppad;
        PADOFFSET refcnt;

        while (--n >= 0) {
          /* If you add a ->what type here, update the comment in regcomp.h */
            switch (r->data->what[n]) {
            case 's':
                SvREFCNT_dec((SV*)r->data->data[n]);
                break;
            case 'f':
                Safefree(r->data->data[n]);
                break;
            case 'p':
                new_comppad = (AV*)r->data->data[n];
                break;
            case 'o':
                if (new_comppad == NULL)
                    Perl_croak(aTHX_ "panic: pregfree comppad");
                PAD_SAVE_LOCAL(old_comppad,
                    /* Watch out for global destruction's random ordering. */
                    (SvTYPE(new_comppad) == SVt_PVAV) ? new_comppad : NULL
                );
                OP_REFCNT_LOCK;
                refcnt = OpREFCNT_dec((OP_4tree*)r->data->data[n]);
                OP_REFCNT_UNLOCK;
                if (!refcnt)
                    op_free((OP_4tree*)r->data->data[n]);

                PAD_RESTORE_LOCAL(old_comppad);
                SvREFCNT_dec((SV*)new_comppad);
                new_comppad = NULL;
                break;
            case 'n':
                break;
            default:
                Perl_croak(aTHX_ "panic: regfree data code '%c'", r->data->what[n]);
            }
        }
        Safefree(r->data->what);
        Safefree(r->data);
    }
    Safefree(r->startp);
    Safefree(r->endp);
    Safefree(r);
}

/*
 - regnext - dig the "next" pointer out of a node
 *
 * [Note, when REGALIGN is defined there are two places in regmatch()
 * that bypass this code for speed.]
 */
regnode *
Perl_regnext(pTHX_ register regnode *p)
{
    register I32 offset;

    if (p == &PL_regdummy)
        return(NULL);

    offset = (reg_off_by_arg[OP(p)] ? ARG(p) : NEXT_OFF(p));
    if (offset == 0)
        return(NULL);

    return(p+offset);
}

STATIC void     
S_re_croak2(pTHX_ const char* pat1,const char* pat2,...)
{
    va_list args;
    STRLEN l1 = strlen(pat1);
    STRLEN l2 = strlen(pat2);
    char buf[512];
    SV *msv;
    const char *message;

    if (l1 > 510)
        l1 = 510;
    if (l1 + l2 > 510)
        l2 = 510 - l1;
    Copy(pat1, buf, l1 , char);
    Copy(pat2, buf + l1, l2 , char);
    buf[l1 + l2] = '\n';
    buf[l1 + l2 + 1] = '\0';
#ifdef I_STDARG
    /* ANSI variant takes additional second argument */
    va_start(args, pat2);
#else
    va_start(args);
#endif
    msv = vmess(buf, &args);
    va_end(args);
    message = SvPV_const(msv,l1);
    if (l1 > 512)
        l1 = 512;
    Copy(message, buf, l1 , char);
    buf[l1-1] = '\0';                   /* Overwrite \n */
    Perl_croak(aTHX_ "%s", buf);
}

/* XXX Here's a total kludge.  But we need to re-enter for swash routines. */

void
Perl_save_re_context(pTHX)
{

    struct re_save_state *state;

    SAVEVPTR(PL_curcop);
    SSGROW(SAVESTACK_ALLOC_FOR_RE_SAVE_STATE + 1);

    state = (struct re_save_state *)(PL_savestack + PL_savestack_ix);
    PL_savestack_ix += SAVESTACK_ALLOC_FOR_RE_SAVE_STATE;
    SSPUSHINT(SAVEt_RE_STATE);

    state->re_state_reg_flags = PL_reg_flags;
    state->re_state_bostr = PL_bostr;
    state->re_state_reginput = PL_reginput;
    state->re_state_regbol = PL_regbol;
    state->re_state_regeol = PL_regeol;
    state->re_state_regstartp = PL_regstartp;
    state->re_state_regendp = PL_regendp;
    state->re_state_reglastparen = PL_reglastparen;
    state->re_state_reglastcloseparen = PL_reglastcloseparen;
    state->re_state_regtill = PL_regtill;
    state->re_state_reg_start_tmp = PL_reg_start_tmp;
    state->re_state_reg_start_tmpl = PL_reg_start_tmpl;
    state->re_state_reg_eval_set = PL_reg_eval_set;
    state->re_state_regnarrate = PL_regnarrate;
    state->re_state_regindent = PL_regindent;
    state->re_state_reg_call_cc = PL_reg_call_cc;
    state->re_state_reg_re = PL_reg_re;
    state->re_state_reg_ganch = PL_reg_ganch;
    state->re_state_reg_sv = PL_reg_sv;
    state->re_state_reg_match_utf8 = PL_reg_match_utf8;
    state->re_state_reg_magic = PL_reg_magic;
    state->re_state_reg_oldpos = PL_reg_oldpos;
    state->re_state_reg_oldcurpm = PL_reg_oldcurpm;
    state->re_state_reg_curpm = PL_reg_curpm;
    state->re_state_reg_oldsaved = PL_reg_oldsaved;
    state->re_state_reg_oldsavedlen = PL_reg_oldsavedlen;
    state->re_state_reg_maxiter = PL_reg_maxiter;
    state->re_state_reg_leftiter = PL_reg_leftiter;
    state->re_state_reg_poscache = PL_reg_poscache;
    state->re_state_reg_poscache_size = PL_reg_poscache_size;
    state->re_state_regsize = PL_regsize;
    state->re_state_reg_starttry = PL_reg_starttry;

    /* These variables have been eliminated from 5.10:  */
    state->re_state_regdata = PL_regdata;
    state->re_state_regprogram = PL_regprogram;
    state->re_state_regcc = PL_regcc;
    state->re_state_regprecomp = PL_regprecomp;
    state->re_state_regnpar = PL_regnpar;

    PL_reg_start_tmp = 0;
    PL_reg_start_tmpl = 0;
    PL_reg_oldsaved = NULL;
    PL_reg_oldsavedlen = 0;
    PL_reg_maxiter = 0;
    PL_reg_leftiter = 0;
    PL_reg_poscache = NULL;
    PL_reg_poscache_size = 0;

    /* Save $1..$n (#18107: UTF-8 s/(\w+)/uc($1)/e); AMS 20021106. */
    if (PL_curpm) {
        const REGEXP * const rx = PM_GETRE(PL_curpm);
        if (rx) {
            U32 i;
            for (i = 1; i <= rx->nparens; i++) {
                GV *gv;
                char digits[TYPE_CHARS(long)];
                const STRLEN len = my_snprintf(digits, sizeof(digits), "%lu", (long)i);
                GV *const *const gvp
                    = (GV**)hv_fetch(PL_defstash, digits, len, 0);

                if (gvp && SvTYPE(gv = *gvp) == SVt_PVGV && GvSV(gv)) {
                    save_scalar(gv);
                }
            }
        }
    }
}

static void
clear_re(pTHX_ void *r)
{
    ReREFCNT_dec((regexp *)r);
}

#ifdef DEBUGGING

STATIC void
S_put_byte(pTHX_ SV *sv, int c)
{
    if (isCNTRL(c) || c == 255 || !isPRINT(c))
        Perl_sv_catpvf(aTHX_ sv, "\\%o", c);
    else if (c == '-' || c == ']' || c == '\\' || c == '^')
        Perl_sv_catpvf(aTHX_ sv, "\\%c", c);
    else
        Perl_sv_catpvf(aTHX_ sv, "%c", c);
}


STATIC const regnode *
S_dumpuntil(pTHX_ const regnode *start, const regnode *node,
            const regnode *last, SV* sv, I32 l)
{
    register U8 op = EXACT;     /* Arbitrary non-END op. */
    register const regnode *next;

    while (op != END && (!last || node < last)) {
        /* While that wasn't END last time... */

        NODE_ALIGN(node);
        op = OP(node);
        if (op == CLOSE)
            l--;        
        next = regnext((regnode *)node);
        /* Where, what. */
        if (OP(node) == OPTIMIZED)
            goto after_print;
        regprop(sv, (regnode *) node);
        PerlIO_printf(Perl_debug_log, "%4"IVdf":%*s%s", (IV)(node - start),
                      (int)(2*l + 1), "", SvPVX_const(sv));
        if (next == NULL)               /* Next ptr. */
            PerlIO_printf(Perl_debug_log, "(0)");
        else
            PerlIO_printf(Perl_debug_log, "(%"IVdf")", (IV)(next - start));
        (void)PerlIO_putc(Perl_debug_log, '\n');
      after_print:
        if (PL_regkind[(U8)op] == BRANCHJ) {
            register const regnode *nnode = (OP(next) == LONGJMP
                                             ? regnext((regnode *)next)
                                             : next);
            if (last && nnode > last)
                nnode = last;
            node = dumpuntil(start, NEXTOPER(NEXTOPER(node)), nnode, sv, l + 1);
        }
        else if (PL_regkind[(U8)op] == BRANCH) {
            node = dumpuntil(start, NEXTOPER(node), next, sv, l + 1);
        }
        else if ( op == CURLY) {   /* "next" might be very big: optimizer */
            node = dumpuntil(start, NEXTOPER(node) + EXTRA_STEP_2ARGS,
                             NEXTOPER(node) + EXTRA_STEP_2ARGS + 1, sv, l + 1);
        }
        else if (PL_regkind[(U8)op] == CURLY && op != CURLYX) {
            node = dumpuntil(start, NEXTOPER(node) + EXTRA_STEP_2ARGS,
                             next, sv, l + 1);
        }
        else if ( op == PLUS || op == STAR) {
            node = dumpuntil(start, NEXTOPER(node), NEXTOPER(node) + 1, sv, l + 1);
        }
        else if (op == ANYOF) {
            /* arglen 1 + class block */
            node += 1 + ((ANYOF_FLAGS(node) & ANYOF_LARGE)
                    ? ANYOF_CLASS_SKIP : ANYOF_SKIP);
            node = NEXTOPER(node);
        }
        else if (PL_regkind[(U8)op] == EXACT) {
            /* Literal string, where present. */
            node += NODE_SZ_STR(node) - 1;
            node = NEXTOPER(node);
        }
        else {
            node = NEXTOPER(node);
            node += regarglen[(U8)op];
        }
        if (op == CURLYX || op == OPEN)
            l++;
        else if (op == WHILEM)
            l--;
    }
    return node;
}

#endif  /* DEBUGGING */

/*
 * Local variables:
 * c-indentation-style: bsd
 * c-basic-offset: 4
 * indent-tabs-mode: t
 * End:
 *
 * ex: set ts=8 sts=4 sw=4 noet:
 */