[IncandescentGas]

Learned regex in the 90's from the Perl documentation, or possibly one of the oreilly perl references. That was a time where printed language references were more convenient than searching the internet. Perl still includes a shell component for accessing it's documentation, that was invaluable in those ancient times. Perl's regex documentation is rather fantastic.

`perldoc perlre` from your terminal.

or https://perldoc.perl.org/perlre

A simple way to test a regex you're building is this website, which offers immediate parsing and documentation of your regex, lets you test it against various inputs, and lets you choose which language's regex parser you are targeting.

https://regexr.com/