325
Oh boy what a beautiful regex. I'm sure it does something logical and easy to understand.
(lemmy.world)
^.?$|^(..+?)\1+$
Matches strings of any character repeated a non-prime number of times
Yeah, I've found myself wasting quite a lot of time thinking of the 'perfect regex' for task X only to realise that I could have avoided doing so by simply taking a different approach.