(?: strings|stringb|stringc)

Is valid regex given a list of strings to match, no?

Is the advantage here some performance gain or potential to use fewer characters depending on the list?

Edit: I see elsewhere it's specifically so you can match against a long list of specific IPs - so maybe a bit of both.

I see. Even if I have no use case for it personally, I want you to thank you for sharing. Its probably a niche use case, but always interesting to see what problems others try to solve and how they did it. The code is actually smaller than I expected.