Good catch on the $email variable in the example. It's pretty useless in the error message. :)

As for $class, the Validate->email() call is actually a class method call. You can read it as "call the email method of the Validate class".

Due to the way Perl's OO works, the invocant (the noun: a class or object) you're asking to perform the verb (the method) is passed as the first argument to the method. In an object method call, you'd get the object as the first p arameter. In a class method call, you get the class name.

perloot and perlboot have more details.