I think you meant "(arse|ass)?holes".

"arseassarseholes"?!

Taking your question at face value, some people say "arseholes", some people say "assholes", and some people just say "holes". We can factor out the "holes" to get that some people say "arse", some people say "ass", and some say nothing extra. We get alternation in regular expressions by separating them with a vertical bar, so we have a regular expression:

    arse | ass

That's optional, so we have the regular expression:

    (arse|ass)+

Put back the "holes" and we get the regular expression:

    (arse|ass)+holes

Clear?

Taking your confusion at face value, what you should have done is to use a question mark ‘?’ instead of a plus sign ‘+’. Otherwise, the string which oneeyedpigeon posted also matches your regexp.

Hah! That explains it! Yes, the "+" usually means "1 or more" rather than the "optional" which I assumed. I rarely use either, because in my computing history I've used RexExp engines that didn't use those symbols consistently.

I'll leave my comment there as a testament to writing from memory and experience, rather than taking the time to check modern standards, and how things might have changed.

Thank you.

Now we have 2 problems.

(arse|ass){0,1}holes

Is how i would write it, +/- a case insensitive flag.

It's legit. https://regex101.com/r/qY0tO9/1