use warnings;
use strict;

my $xyz = 0;
if($xyz) { eval { $main::globalvar = undef; print STDERR __LINE__, ": eval'd\n"} }
printf "%d: if(%d) => didn't eval\n", __LINE__, $xyz;
$xyz = 1;
if($xyz) { eval { $main::globalvar = undef; print STDERR __LINE__, ": eval'd\n"} }
printf "%d: if(%d) => did eval => '%s'\n", __LINE__, $xyz, defined $main::globalvar ? $main::globalvar : '<undef>';