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.