use strict;
use warnings;
no warnings 'uninitialized';

## not recommended
use Scalar::Util 'dualvar';

my ($test, $test2);

print sprintf('1: %s', $test), "\n";

if (not defined $test) {
    $test = dualvar(0, 'OK');
    print sprintf('2: %s', $test), "\n";
}

print sprintf('3: %s', $test > 1 ? $test : undef), "\n";

if (not defined $test2) {
    print sprintf('4: %s', $test), "\n";
}

__END__