Languages invented after Perl will generally use some flavor of Perl regex syntax, but there are always some minor differences. The issue of the meaning of `$` and changing it via multi-line mode is usually consistent though.
I do wonder though what's the highest number of different regex syntaxes I've ever encountered (perhaps written?) within a single line: bash, grep and sed are never not in a "hold my beer" mood!
They seem to improve. Negative lookbehind isn't missing anymore [1]. But still lack the handy \Q and \E to escape stuff [2].
Your comment is missing a trigger warning, lol. But seriously, this is one of my flags for "this should probably be a script, or an awk or perl one-liner."
I've got "hold my beer" commits in .net - I've balanced brackets. I believe that's impossible in sed and grep. If I were going to write a json parser in a script, then a) stop me and b) it's got to be in powershell.