use strict; sub This::Does::Not::Fail { }; # Rightly so because you've already notified Perl that # this is a subroutine name. It *knows* this identifier # is a sub. Thanks for pre-declaring it! This::Does::Not::Fail; # rightly so # This fails because you've given perl no contextual hints # that this is a subroutine. It might be... a filehandle! # Or something else. But you haven't pre-declared it # either. This is a bareword (an identifier). This::Will::Fail; # as we expect # You haven't pre-declared this thing. # *BUT* you did give perl a contextual hint that this is # indeed a subroutine. This is essentially a *promise* # you've made to strict that at runtime, when this code is # encountered, you'll have a subroutine with this name # all ready to go. It::Bothers::Me::That::This::Works (); # wassup with THAT?!