Note that you can train and test regexes on pages like regex101.com, or locally (visual-regexp). Perhaps with incomplete coverage of the rules, txt2regex can help you to construct regexes for use in awk, emacs, python, vim by answering a few questions. The last two possibly already are packaged for your instance of Linux (repology's query about visual-regexp, and txt2regex). Source: over 1 year ago

BUT - As far as resources for building out the regex patterns, I use regexpal.com and a copy of this https://cheatography.com/davechild/cheat-sheets/regular-expressions/pdf/ printed out beside me. Once you get into it, the power of subgroups, and lookahead/behind processing beats some of the mental gymnastics you would need to go to code it out in your language of choice. Source: almost 2 years ago

Spend an afternoon really diving into it, bookmark regexpal.com, and call it a day IMO. Source: about 2 years ago

i’m a professional developer and I just relearn it every time I need it, which is about once or twice a year, but depending on someone’s specialty they may swim around in it all day. It can get really complicated. https://regexpal.com is where I kick it around testing until it works. Source: about 2 years ago