Recently I've encountered some code hidden in a 1000-line long file that looked like this:

examples/return_or.pl

use strict;

sub compute {
    my ($param) = @_;

    # ...
    return $param or 'default';
}

print '1: ', compute('hello'), "\n";
print '2: ', compute(''), "\n";

I am not even sure how I noticed it, but it looked incorrect so I created the above simple example.