eval "require RT::Ticket_Overlay";
if ($@ && $@ !~ qr{^Can't locate RT/Ticket_Overlay.pm}) {
    die $@;
};

##</code><code>##

#!/usr/bin/env perl -l

use strict;
use warnings;

print $::{'Foo::'} || 'Not found';
eval "use Foo";
print $::{'Foo::'} || 'Not found';
eval "require Foo";
print $::{'Foo::'} || 'Not found';
__END__
Not found
Not found
*main::Foo::

##</code><code>##

print defined *NoSuchModule::ISA{ARRAY} ? 'Yes' : 'No';
print defined *NoSuchModule::xxx{ARRAY} ? 'Yes' : 'No';