True, but see, all these build up on the theoretical regex. The theoretical regex indeed has only 3 operators: dot for concatenation, pipe for alteration and the ‘kleene star’ [re: Sipser’s]. These 3 operators can express a finite state automata. You don’t really need all that other operators. Read this: swtch.com/~rsc/regexp/regexp1.html Algorithms like Thompson construction can translate a regex to a non-deterministic automata quite quickly, and then from there you can make a DFA or just simulate the NFA.
I would not call PCRE ‘regular expression’ really. If you read the article I gave you it explains why they are mostly a practical utility than a theoretical groundwork. The regex in use today is far from the regex one learns about in books.
I think regex is abused. People use it to parse context-free grammars. Extremely intricate and feature-rich patterns cause people to make mistakes, and end up with security holes!
That being said, I really enjoy NeoVim’s regex. I also like Perl’s. But I would not rely on them for parsing, or even lexing.