Oh and dont forget that just because the documentation says it uses a specific regex syntax, that does not mean its correctly implemented. It gets worse when an application examples specify a specific syntax but what happens in the background is that it will use the default reg exp engine, which can be system or enviroment specified.

I just don't count those cases as 'basic' syntax.

Basic - naming a capture group. Awk / posix - \1 Perl - $1. Python - (?P<name>).

I’d find it hard to ignore the specifics. I mean if you only ever use one tool and were never exposed to other regex engines I guess.