Oh dear. Before uploading or even writing Class::Null, as with any other class, I've searched CPAN for a module that would do what I needed. But Sean Burke's Class::BlackHole somehow escaped me. It seems to do pretty much what Class::Null does, except that Class::Null is even more minimalistic. Maybe I just scanned the list for things like 'Null' because I was thinking of the Null pattern...
And Class::Void isn't too dissimilar either. Oh well.