This is a bug report for perl from mons@cpan.org,
generated with the help of perlbug 1.39 running under perl 5.12.0.


-----------------------------------------------------------------
[Please describe your issue here]

##### sample.pl #####
use utf8;
my @make;
while (<DATA>) {
        chomp;
        push @make, '';
        s{\\\s*$}{};
        $make[-1] .= $_;
}
for (@make) {
        m{^([^=]+?)\s*=\s*(.+)$}o;
}
__DATA__
A=      
AAAA=\
### end sample.pl ###

or 

##### sample.pl #####
my @x = ("A=B","AAAA=/");
utf8::upgrade $_ for @x;
$x[1] =~ s{/\s*$}{};
for (@x) {
        m{^([^=]+?)\s*=.+$};
}
### end sample.pl ###

Assertion failed: (rx->sublen >= (s - rx->subbeg) + i), function Perl_reg_numbered_buff_fetch, file regcomp.c, line 5199.
Abort trap: 6 (core dumped)

Repeatable under:
  - v5.10.1 (*) built for i686-linux-thread-multi
  - v5.10.0 built for amd64-freebsd
  - v5.10.1 (*) built for amd64-freebsd
  - v5.12.0 built for amd64-freebsd
  - v5.13.2 built for amd64-freebsd

[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=core
    severity=medium
---
Site configuration information for perl 5.12.0:

Configured by mons at Fri May  7 14:44:18 MSD 2010.

Summary of my perl5 (revision 5 version 12 subversion 0) configuration:
   
  Platform:
    osname=freebsd, osvers=7.1-release-p2, archname=amd64-freebsd
    uname='freebsd veda.park.rambler.ru 7.1-release-p2 freebsd 7.1-release-p2 #0: thu feb 12 22:34:21 msk 2009 root@veda.park.rambler.ru:usrobjusrsrcsysdevel amd64 '
    config_args='-des -Dprefix=/home/mons -Duse64bitint -DDEBUG_LEAKING_SCALARS -DDEBUGGING -Dinc_version_list=none -Dccflags=-O2 -march=athlon64 -fomit-frame-pointer -pipe -ggdb -g3 -Doptimize=-O2 -g3'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=undef, usemultiplicity=undef
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-O2 -march=athlon64 -fomit-frame-pointer -pipe -ggdb -g3 -DHAS_FPSETMASK -DHAS_FLOATINGPOINT_H -DDEBUGGING -fno-strict-aliasing -fstack-protector -I/usr/local/include',
    optimize='-O2 -g3',
    cppflags='-O2 -march=athlon64 -fomit-frame-pointer -pipe -ggdb -g3 -DHAS_FPSETMASK -DHAS_FLOATINGPOINT_H -DDEBUGGING -fno-strict-aliasing -fstack-protector -I/usr/local/include'
    ccversion='', gccversion='4.2.1 20070719  [FreeBSD]', gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
    ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='cc', ldflags ='-Wl,-E  -fstack-protector -L/usr/local/lib'
    libpth=/usr/lib /usr/local/lib
    libs=-lgdbm -lm -lcrypt -lutil -lc
    perllibs=-lm -lcrypt -lutil -lc
    libc=, so=so, useshrplib=false, libperl=libperl.a
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags=' '
    cccdlflags='-DPIC -fPIC', lddlflags='-shared  -L/usr/local/lib -fstack-protector'

Locally applied patches:
    

---
@INC for perl 5.12.0:
    /home/mons/perl/perl-ex
    /home/mons/lib/perl5/site_perl/5.12.0/amd64-freebsd
    /home/mons/lib/perl5/site_perl/5.12.0
    /home/mons/lib/perl5/5.12.0/amd64-freebsd
    /home/mons/lib/perl5/5.12.0
    .

---
Environment for perl 5.12.0:
    HOME=/home/mons
    LANG=en_US.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/mons/home-bin:/home/mons/bin:/home/mons/flex/bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/games:/usr/local/sbin:/usr/local/bin:/home/mons/bin
    PERL5LIB=/home/mons/perl/perl-ex
    PERL_BADLANG (unset)
    SHELL=/usr/local/bin/bash