I think it's just a distinction between a factory method and a constructor. Perl gives you factory methods. You have to explicitly return your 'object' at the very end of your 'constructor'. Whereas the traditional notion of a constructor is something that implicitly returns itself and all you need to do is ensure that your object is in a suitable initial state.

Factory methods are just as flexible though and I usually favor them over constructors anyway since they give you a lot more control over what specific object you are creating. For instance, a factory method can create and return a specific subtype of the object you want and you can swap out that specific subtype (to change underlying implementation) easily without breaking client code. Similarly with turning a class into a singleton.