Regex Isn’t Hard - Tim Kellogg 👈 this is a pretty good conscience article on regexes, and I agree, regex isn’t that hard™ – However I think I can make the TL;DR even shorter 😅
Regex core subset (portable across languages):
Character sets
• a matches “a”
• [a-z] any lowercase
• [a-zA-Z0-9] alphanumeric
• [^ab] any char but a or b
Repetition (applies to the preceding atom)
• ? zero or one
• * zero or more
• + one or more
Groups
• (ab)+ matches “ab”, “abab”, …
• Capture for extract/substitute via $1 or \1
Operators
• foo|bar = foo or bar
• ^ start anchor
• $ end anchor
Ignore non‑portable shortcuts: \w, ., {n}, *?, lookarounds.