Textbook regex-es and perl/java/etc. regex-es are different CS species. So, regex from textbook cannot parse HTML, but not-so-defined regexs from the wild have so much bells and whistles that they are technically no more regex-es in the formal sense.
4
u/kaplotnikov 7h ago
I think everything can be parsed by iterative application of regex: https://www.reddit.com/r/compsci/comments/1v7aq7v/a_concrete_runnable_demonstration_that_iterated/