This problem originally occured while running tests for installing
Test::Harness, but I've been able to replicate it independently. For
reference, the original ticket is available at
http://rt.cpan.org/NoAuth/Bug.html?id=6452.
The problem is that an local environment variable set in an anonymous block
seems to be available to child processes created afterwards using qx(). I
have not tested this using system() or fork(). See the example scripts
below.
test1.pl
#!/usr/bin/perl -w
use warnings;
use strict;
my $key = "WANGO";
BLOCK1: {
my $val = $ENV{$key};
$val = "undef" unless defined $val;
print "In BLOCK1, \$ENV{$key} = [$val]\n";
}
BLOCK2: {
local $ENV{$key} = "FOTANGO";
my $val = $ENV{$key};
$val = "undef" unless defined $val;
print "In BLOCK2, \$ENV{$key} = [$val]\n";
}
BLOCK3: {
my $val = qx/test2.pl/;
$val = "undef" unless defined $val;
print "In BLOCK3, \$ENV{$key} = [$val]\n";
print " ... BUT IT SHOULD BE undef!" unless $val eq "undef";
}
=cut
test2.pl
#!/usr/bin/perl -w
use strict;
my $val = $ENV{WANGO};
$val = "undef" if ! defined $val;
print $val;
=cut
My results on Cygwin are...
In BLOCK1, $ENV{WANGO} = [undef]
In BLOCK2, $ENV{WANGO} = [FOTANGO]
In BLOCK3, $ENV{WANGO} = [FOTANGO]
... BUT IT SHOULD BE undef!
On Linux (Perl 5.8.4 on Gentoo with a 2.4.26 kernel), Win32 (ActiveState Build
810), HP-UX (Perl 5.8.0), and Mac OS X (Perl 5.8.0), the results are...
In BLOCK1, $ENV{WANGO} = [undef]
In BLOCK2, $ENV{WANGO} = [FOTANGO]
In BLOCK3, $ENV{WANGO} = [undef]
Adding an "$ENV{WANGO} = undef;" to the end of BLOCK2 seems to take care of
the problem, but coding this way for just one platform doesn't seem quite
right to me. I'm also not sure if this is actually a problem with Perl or an
issue with Cygwin itself.
Regards,
Steve Peters
steve@fisharerojo.org
