Regexes are a cool and important part of your Perl-toolchest. But as with any tool, one must use it wisely.

In this case, you want to distinguish between "good" and "bad" words. Sometimes it is easy to define what is "good" and sometimes it is more easy to define what is "bad".

In this particular case, the definition of a good word is easy: 7 zeroes followed by a digit. It then follows logically that all words that to not comply with this simple format must be "bad". Hence we extract all "good" words and simply drop all others and we don't care in which way they may be bad.

The only regex you need is therefore qr/0{7}\d/ and depending on how the words are presented to you, you may wish to "anchor" the regex in the front or the back to avoid some false positives.

By concentrating upon the "bad" words you made it yourself unnecessary difficult.