[ID 20000413.003] Script fails for all perl versions after 5.005_02

This is a bug report for perl from friebel@desy.de,
generated with the help of perlbug 1.28 running under perl v5.6.0.


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[Please enter your report here]
The following stripped down perl script is working correctly under
any perl version available to me up to perl 5.005_02. I tried vendor
supplied versions and versions compiled myself (Solaris and Linux)
starting with 5.001 through 5.6.0 (the latter one with and without
thread support) 
The script should print an empty line followed by two lines "SUBROUTINE"
This is the intended behaviour and was working properly until 5.005_02

After that depending on the value of $test in the first line the third
line is

incorrectly printed as the value of $test (matching expr)

or giving a warning under perl -w:
Use of uninitialized value in concatenation (.) at search.cgi line 8, <DATA> line 3.

Stripping the script further down seems to make the misbehaviour vanish.
The script search.cgi:
# Author: F Schrempp
$test='a2a';
$test='bbb' if $test =~ /aaa/;
$var = 'abc';
$tagnam = "";
while (<DATA>) {
  if (/SUBROUTINE/../END/){
    print "$tagnam\n" if defined $&;
    $tagnam = $&;
    next if (!/$var/);
  }
}
close(DATA);
__END__
SUBROUTINE HVHBVI
PHEP
END
[Please do not change anything below this line]
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---
Flags:
    category=core
    severity=medium
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Site configuration information for perl v5.6.0:

Configured by friebel at Tue Apr 11 17:48:23 MET DST 2000.

Summary of my perl5 (revision 5.0 version 6 subversion 0) configuration:
  Platform:
    osname=solaris, osvers=2.6, archname=sun4-solaris-thread
    uname='sunos ilos 5.6 generic_105181-16 sun4u sparc sunw,ultra-4 '
    config_args=''
    hint=previous, useposix=true, d_sigaction=define
    usethreads=define use5005threads=define useithreads=undef usemultiplicity=undef
    useperlio=undef d_sfio=undef uselargefiles=define 
    use64bitint=undef use64bitall=undef uselongdouble=undef usesocks=undef
  Compiler:
    cc='cc', optimize='-O', gccversion=
    cppflags='-D_REENTRANT -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64'
    ccflags ='-D_REENTRANT -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64'
    stdchar='unsigned char', d_stdstdio=define, usevfork=false
    intsize=4, longsize=4, ptrsize=4, doublesize=8
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=8, usemymalloc=y, prototype=define
  Linker and Libraries:
    ld='cc', ldflags ='-L/usr/local/lib -R/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib /usr/ccs/lib
    libs=-lsocket -lnsl -lgdbm -ldb -ldl -lm -lposix4 -lpthread -lc -lcrypt -lsec
    libc=/lib/libc.so, so=so, useshrplib=false, libperl=libperl.a
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags=' '
    cccdlflags='-KPIC', lddlflags='-G -L/usr/local/lib'

Locally applied patches:
    

---
@INC for perl v5.6.0:
    /products/perl/5.6.0/lib/sun4-solaris-thread
    /products/perl/5.6.0/lib
    /products/perl/5.6.0/lib/site_perl/sun4-solaris-thread
    /products/perl/5.6.0/lib/site_perl
    /products/perl/5.6.0/lib/site_perl
    .

---
Environment for perl v5.6.0:
    HOME=/home/jupiter/friebel
    LANG=C
    LANGUAGE (unset)
    LD_LIBRARY_PATH=/usr/openwin/lib:/usr/dt/lib:/usr/local/lib
    LOGDIR (unset)
    PATH=/products/perl/5.6.0/bin:/home/jupiter/friebel/bin.SunOS_5:/home/jupiter/friebel/bin.SunOS:/home/jupiter/friebel/bin:/home/jupiter/friebel/scripts:/usr/sue/bin:/usr/bin:/usr/ucb:/usr/sbin:/opt/SUNWspro/bin:/usr/ccs/bin:/usr/openwin/bin:/usr/local/X11/bin:/usr/local/bin:/usr/local/bin/scripts::.:/cern/pro/bin
    PERL_BADLANG (unset)
    SHELL=/bin/zsh

• [ID 20000413.003] Script fails for all perl versions after 5.005_02 by Wolfgang Friebel
• Re: [ID 20000413.003] Script fails for all perl versions after 5.005_02 by Ilya Zakharevich