Use it for finding email addresses or checking if something is email like. You shouldn't use this for validating emails. Only for hinting to the user. If you run the regex against untrusted user input ...

Ever wished you could instantly extract all email addresses from a document or clean up messy data with a single command? Regex makes that possible. Regular expressions (often shortened to “regex”) ...

PCRE2 is the name used for a revised API for the PCRE library, which is a set of functions, written in C, that implement regular expression pattern matching using the same syntax and semantics as Perl ...