if you have an edge case you know you want, you could add the description into the input of the AI.

If you are afraid of unintended matches, that's a different problem, which you might also get writing the regex yourself!

The solution, i reckon, is to create (may be even via the same AI?) a large list of matches, and you manually look thru to see if there's unintended matches.

That's true, but I think it's important to take the encryption approach, I understand how it works vaguely and hope I don't get burned.