String::Checker - An extensible string validation module (allowing commonly
used checks on strings to be called more concisely and consistently).
Why is this useful?  If you're only checking one string, it probably
isn't.  However, if you're checking a bunch of strings (say, for
example, CGI input parameters) against a set of expectations, this
comes in pretty handy.  As a matter of fact, the CGI::ArgChecker
module is a simple, CGI.pm aware wrapper for this library.