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[perl #67694] List::Util attaching to the wrong $_ when used inside given/when construct

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From:
perlbug-followup
Date:
July 19, 2009 09:49
Subject:
[perl #67694] List::Util attaching to the wrong $_ when used inside given/when construct
Message ID:
rt-3.6.HEAD-2466-1248006345-1401.67694-75-0@perl.org
# New Ticket Created by  vparseval@gmail.com 
# Please include the string:  [perl #67694]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=67694 >



This is a bug report for perl from vparseval@gmail.com,
generated with the help of perlbug 1.36 running under perl 5.10.0.


-----------------------------------------------------------------
[Please enter your report here]

Please behold the following:

    #!/usr/bin/perl -l

    use feature     qw/switch/;
    use List::Util  qw/first/;

    my $val = 1;
    given ($val) {

        # my $_
         
        when (1) {
            print +(first { $_ == 10 } 10 .. 15) ? 'works inside when' 
                                                 : 'broken inside when';
        }
    }
    print +(first { $_ == 10 } 10 .. 15) ? 'works outside when' 
                                         : 'broken outside when';
    __END__
    broken inside when
    works outside when

Note that when commenting out the lexical declaration of $_, the code behaves
as expected.

At this point, I am not sure if the problem is in List::Util or the perl core.
List::MoreUtil uses does the same thing as List::Util when it comes to
assigning to $_ and dispatching the code-reference hence it's suffering from 
the same malaise.

Cheers,
Tassilo

[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=library
    severity=low
---
Site configuration information for perl 5.10.0:

Configured by Debian Project at Sun May  3 21:49:06 UTC 2009.

Summary of my perl5 (revision 5 version 10 subversion 0) configuration:
  Platform:
    osname=linux, osvers=2.6.18-xen-3.1-1-amd64, archname=x86_64-linux-gnu-thread-multi
    uname='linux nautilus 2.6.18-xen-3.1-1-amd64 #1 smp fri oct 19 23:35:59 cest 2007 x86_64 gnulinux '
    config_args='-Dusethreads -Duselargefiles -Dccflags=-DDEBIAN -Dcccdlflags=-fPIC -Darchname=x86_64-linux-gnu -Dprefix=/usr -Dprivlib=/usr/share/perl/5.10 -Darchlib=/usr/lib/perl/5.10 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/perl5 -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.10.0 -Dsitearch=/usr/local/lib/perl/5.10.0 -Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1 -Dsiteman3dir=/usr/local/man/man3 -Dman1ext=1 -Dman3ext=3perl -Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Ud_ualarm -Uusesfio -Uusenm -DDEBUGGING=-g -Doptimize=-O2 -Duseshrplib -Dlibperl=libperl.so.5.10.0 -Dd_dosuid -des'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fno-strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O2 -g',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fno-strict-aliasing -pipe -I/usr/local/include'
    ccversion='', gccversion='4.3.3', 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 =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib /lib64 /usr/lib64
    libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
    perllibs=-ldl -lm -lpthread -lc -lcrypt
    libc=/lib/libc-2.9.so, so=so, useshrplib=true, libperl=libperl.so.5.10.0
    gnulibc_version='2.9'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -O2 -g -L/usr/local/lib'

Locally applied patches:
    

---
@INC for perl 5.10.0:
    /etc/perl
    /usr/local/lib/perl/5.10.0
    /usr/local/share/perl/5.10.0
    /usr/lib/perl5
    /usr/share/perl5
    /usr/lib/perl/5.10
    /usr/share/perl/5.10
    /usr/local/lib/site_perl
    .

---
Environment for perl 5.10.0:
    HOME=/home/ethan
    LANG=en_US.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/ethan/bin:/home/ethan/bin:/usr/local/bin:/usr/bin:/bin:/usr/games
    PERL_BADLANG (unset)
    SHELL=/bin/bash


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