Bug#479434: perl: Getopt::Long with subs breaks in Perl 5.10

[Russ Allbery <rra@debian.org>]

Package: perl
Version: 5.10.0-9
Severity: important

Something fairly fundamental appears to have changed about the handling
of variable aliasing and subroutine calls that breaks Getopt::Long with
sub arguments.  Consider the following one-liner, extracted from the
lintian frontend:

perl -MGetopt::Long -e 'my $action; sub set_action { $action = $_[0] } Getopt::Long::GetOptions ("setup-lab" => \&set_action); print "$action\n"; $action = "check" unless $action; print "$action\n"' -- --setup-lab

Getopt::Long calls set_action with two arguments ('setup-lab' and 1)
and $action subsequently stringifies to "setup-lab", but $action appears
to be false for the unless check.  So it's then reassigned to a different
value.  It looks like the state of the $action variable is partly aliased
to $_[0], supported by the fact that the bug disappears if $action is
assigned "$_[0]" instead of just $_[0].

-- System Information:
Debian Release: lenny/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: i386 (i686)

Kernel: Linux 2.6.24-1-686 (SMP w/2 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages perl depends on:
ii  libc6                         2.7-10     GNU C Library: Shared libraries
ii  libdb4.6                      4.6.21-8   Berkeley v4.6 Database Libraries [
ii  libgdbm3                      1.8.3-3    GNU dbm database routines (runtime
ii  perl-base                     5.10.0-9   The Pathologically Eclectic Rubbis
ii  perl-modules                  5.10.0-9   Core Perl modules

Versions of packages perl recommends:
ii  netbase                       4.32       Basic TCP/IP networking system
ii  perl-doc                      5.10.0-9   Perl documentation

-- no debconf information