[burgerbrain]

You can in fact do recursion with regular grammars as you've just demonstrated, but if you mix right regular grammars with left regular grammars (as you would need to do in order to, for example, match parenthesis) your grammar is no longer regular (not equivalent to regular expressions). I suspect that is what wisty meant.

Honestly though, this entire conversation is fuzzed by the blurred distinction between "parsing with regular expressions, and writing a parser that uses regular expressions to tokenize" by the original author. I'm not really sure where just about every other person in this discussion is coming from as a result..