This is a cool feature of a lot of regex implementations but I will warn you that reusing capture groups in a match means it’s impossible for any regex engine to guarantee a reasonable upper bound (best they can do is O(n!) I think? I’d have to look up the details). In a replacement string this is a non-issue because there’s no way they can recurse out of control.

Edit: found the video I originally heard this from: https://www.youtube.com/watch?v=gITmP0IWff0

There is Backus-Naur form (and it’s derivatives), which at least lets you name each section of text like you would a variable or function. Technically matches context-free expressions rather than regular ones but that’s hardly different for most cases.