[perl #24532] "\(?" confuses re engine

# New Ticket Created by  Rob McMillin 
# Please include the string:  [perl #24532]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org/rt2/Ticket/Display.html?id=24532 >


This is a bug report for perl from rlm@pricegrabber.com,
generated with the help of perlbug 1.33 running under perl v5.6.1.


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[Please enter your report here]

Pretty simple: 

\(? doesn't work as expected in a regexp when the enclosing brackets
are themselves parens, as

if ($nonce_str =~ m(\(?r\)?)i) { ... }

I get an error

"Sequence (? ...) not recognized before HERE mark in regex m((?   << HERE r)?/"

which is clearly bogus.  However,


if ($nonce_str =~ m([(]?r[)]?)i) { ... }

works just fine.

[Please do not change anything below this line]
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---
Flags:
    category=core
    severity=medium
---
Site configuration information for perl v5.6.1:

Configured by bhcompile at Mon Apr  1 12:22:19 EST 2002.

Summary of my perl5 (revision 5.0 version 6 subversion 1) configuration:
  Platform:
    osname=linux, osvers=2.4.17-0.13smp, archname=i386-linux
    uname='linux daffy.perf.redhat.com 2.4.17-0.13smp #1 smp fri feb 1 10:30:48 est 2002 i686 unknown '
    config_args='-des -Doptimize=-O2 -march=i386 -mcpu=i686 -Dcc=gcc -Dcf_by=Red Hat, Inc. -Dcccdlflags=-fPIC -Dinstallprefix=/usr -Dprefix=/usr -Darchname=i386-linux -Dvendorprefix=/usr -Dsiteprefix=/usr -Uusethreads -Uuseithreads -Uuselargefiles -Dd_dosuid -Dd_semctl_semun -Di_db -Di_ndbm -Di_gdbm -Di_shadow -Di_syslog -Dman3ext=3pm'
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=undef use5005threads=undef useithreads=undef usemultiplicity=undef
    useperlio=undef d_sfio=undef uselargefiles=undef usesocks=undef
    use64bitint=undef use64bitall=undef uselongdouble=undef
  Compiler:
    cc='gcc', ccflags ='-fno-strict-aliasing -I/usr/local/include',
    optimize='-O2 -march=i386 -mcpu=i686',
    cppflags='-fno-strict-aliasing -I/usr/local/include'
    ccversion='', gccversion='2.96 20000731 (Red Hat Linux 7.2 2.96-109)', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=4
    alignbytes=4, usemymalloc=n, prototype=define
  Linker and Libraries:
    ld='gcc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lnsl -ldl -lm -lc -lcrypt -lutil
    perllibs=-lnsl -ldl -lm -lc -lcrypt -lutil
    libc=/lib/libc-2.2.5.so, so=so, useshrplib=false, libperl=libperl.a
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-rdynamic'
    cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib'

Locally applied patches:
    

---
@INC for perl v5.6.1:
    /home/rlm/backend/libs
    /usr/lib/perl5/5.6.1/i386-linux
    /usr/lib/perl5/5.6.1
    /usr/lib/perl5/site_perl/5.6.1/i386-linux
    /usr/lib/perl5/site_perl/5.6.1
    /usr/lib/perl5/site_perl
    /usr/lib/perl5/vendor_perl/5.6.1/i386-linux
    /usr/lib/perl5/vendor_perl/5.6.1
    /usr/lib/perl5/vendor_perl
    .

---
Environment for perl v5.6.1:
    HOME=/home/rlm
    LANG=en_US.iso885915
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/bin:/usr/bin:/sbin:/usr/sbin:/home/rlm/backend/distributors:/home/rlm/backend/hacks:/home/rlm/backend/libs:/home/rlm/backend/content:/home/rlm/backend/reports:/home/rlm/backend/retailers:/home/rlm/backend/spiders:/home/rlm/backend/utils:/home/rlm/backend/muze:/home/rlm/backend/fastcsv:/home/rlm/backend/exports:/home/rlm/src/perls:/usr/local/bin
    PERL5LIB=/home/rlm/backend/libs
    PERL_BADLANG (unset)
    SHELL=/bin/bash

• [perl #24532] "\(?" confuses re engine by Rob McMillin
• Re: [perl #24532] "\(?" confuses re engine by SADAHIRO Tomoyuki