Regex the "env specific variant" or regex the concept (as it applies to theory of computation) etc? The former I can never remember beyond the basics (*, +, ?,

Regex the "env specific variant" or regex the concept (as it applies to theory of computation) etc? The former I can never remember beyond the basics (*, +, ?, |). Even the | I go extra cautious and put in tons of parenthesis. If I ever need matching and grouping I resort to rtfm. Now that latter, that's the more interesting and fun one!! Learnt it in college decades ago but really drilled it in by reimplementing Russ Cox's amazing Thomson nfa blog and breakdown in typescript!