Regex is a type of pattern used to search a text string or sequence of characters for a match. Have you ever wondered how websites can tell you that the email pattern you have entered on a login ...

Once you get the hang of regular expressions, you'll find them invaluable. The trick is to start small - I'll show you how.

The Internet has many regex resources, allowing you to learn ... a 'hat' inside a character class [^LIKETHIS] inverts the match. (Must NOT be any of the characters in the box).

I might write [Hh]ack ?a ?[Dd]ay as a regular expression to match things like “HackaDay” and “Hack a day” and, even, “Hackaday” using a tool like grep, awk, or many programming languages.