As it turns out, it appears that your code is also not repecting the "all letters in the mystery word are covered by letters in the hint words" rule.

'octopus' is not a solution to your second puzzle because 'u' does not appear in the hint words:

$length = 7;
$hints = {
           'shortest' => '3',
           'drilling' => '0',
           'locked' => '2',
           'messing' => '1',
           'irritated' => '1',
           'glory' => '1',
           'modes' => '2',
           'transcribed' => '3'
         };
[download]

limbic~region's challenge is definitely more complicated than it first appears.

I believe that I finally have my pure regex solution working.