Holy overengineering, Batman. IP addresses of all things are trivially parseable into fixed-length byte sequences. Just do that and use a search tree. Or, IDK; this is an extremely solved problem, there are probably even better solutions out there -- but I promise you text regex is involved in none of the good ones.

Even for actual string matching, any decent regex engine will compile and optimise an alternation a|b|c|... better than this text wrangling will. Unless you have actual benchmarks showing this gives you an advantage with the engine you're using, you're just introducing complexity for no gain.

It's called "allowlist" and "denylist" nowadays as it's easier to understand for non-native speakers and not racist.

I feel like there's an easier and faster way to match IP addresses than regex, e.g. the search tree apparia suggested. At least use bytes to match 😄