It's very important to understand how Perl implemented its "object-oriented" features – what bless actually does, what the "arrow" operator does in various contexts, and so on. Perl-5 is a language that evolved over a long period of time to become what it now is, and it did so without losing backward compatibility with itself. (Perl-6 is not, but Perl-6 never went anywhere and never will.) The Perl Gods never went back into the compiler and added a bunch of new syntax diagrams. If you compare it to "object-oriented" languages that were designed from the ground up to be that way, you'll find that it is not a very close comparison at all. "Object-oriented Perl" really is a very different thing. Moose is implemented in classic Perl – it is not a compiler feature – and can be switched-on use Moose and switched-off no Moose in mid-flight.