I find this to be an interesting side effect of computer science as a branch of mathematics vs applied computer science in "programming" and "development".

I remember touring the computer science building at the university I would end up attending before I had enrolled there - some students in one room were discussing whether there was a regular expression for detecting prime numbers. I laughed to myself - because in my mind, that's not at all what a regular expression was.

Sure enough, there is in fact such a regular expression (or "regex pattern", if you prefer)[1]. Regular expressions in practice encompass BOTH the academic level-3 regular grammar stuff, and a bunch of other stuff that's been tacked on because it's useful in real-world applications.

[1] - This has been posted on HN before, probably a bunch of times: https://iluxonchik.github.io/regular-expression-check-if-num...