print Dumper find_joins( apple => 'dog' );

[] apple => dog at tmp.pl line 31.
[apple] bug => dog at tmp.pl line 31.
[apple] cat => dog at tmp.pl line 31.
$VAR1 = [
          'apple',
          'dog'
        ];
$VAR2 = [
          'apple',
          'bug',
          'dog'
        ];