Can't call method "STORE" on an undefined value during global destruction. Happens under Perl 5.10 (activestate build 1002) and the latest version of Win32::GUI (V1.6 ppm and mingw built version).
The script below shows the issue. It's an odd script, as it's been cut down from a larger test case. Commenting out any of the lines removes the error messages - this is because it changes the order in which the Win32::GUI objects are destroyed.
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use Win32::GUI();
use strict;
my @rows;
for (0..250) { push @rows,'abc'; }
my $win = new Win32::GUI::Window (-name => "win");
$win->Hook(32768+3,sub {});
my $label = $win->AddLabel(-name => "abc");
#print "$win $label\n";
sub Message3 {$win->Hide();};