Regular expressions are common in the programming world as a way of finding (and filtering) text based on patterns. regexes can range from extremely simple, such as the example above for finding whitespaces, to longer expressions for more general inputs. If you are one of the wizards who can actually comprehend phrases like
(?<=^|(?<=[^a-zA-Z0-9-_\.]))@([A-Za-z]+[A-Za-z0-9]+) (a regex for identifying Twitter usernames), then Google Docs' latest feature is just for you.