NotesNo, I’m not joking. Just send your users an email. The activation email is a practice that’s been in use for years, but it’s often paired with complex validations that the email is formatted correctly. If you’re going to send an activation email to users, why bother using a gigantic regular expression?FeedUnfurl
Notes"This Java package contains a DFA/NFA (finite-state automata) implementation with Unicode alphabet (UTF16) and support for the standard regular expression operations (concatenation, union, Kleene star) and a number of non-standard ones (intersection, compUnfurl