Most of your life's problems can be solved at CPAN. :-) Just write:

  use Method::Signatures::Simple;

http://search.cpan.org/~rhesa/Method-Signatures-Simple-1.02/...

But you might instead want to look at this (or similar with Moose support) to get simple type declarations:

http://search.cpan.org/~barefoot/Method-Signatures-20120523/...