Regex is more a technique than an actual specification. It would be best to find the time to go and read an introductory book about Theory of Computation where they explain the underlying mechanism.
It's half a chapter in most books I know. Or a subset of this 1h MIT videos [0], but the instructor also explains Finite Automata which is the basic mechanism that does all the stuff.
I'll assume sarcasm (from your comment history) but for people actually believing this first degree: good luck debugging an incorrect regex if you haven't practiced regexes. Especially if it was generated by an llm.
