And also (and definitely not last!) there is Method::Signatures (http://search.cpan.org/dist/Method-Signatures/ http://search.cpan.org/dist/Method-Signatures/)

And also (and definitely not last!) there is Method::Signatures (http://search.cpan.org/dist/Method-Signatures/ http://search.cpan.org/dist/Method-Signatures/) which adds both function & method signatures.