Method::Signatures provides two new keywords, func and method, so that you can write subroutines with signatures instead of having to spell out my $self = shift; my($thing) = @_ func is like sub but takes a signature where the prototype would normally go. This takes the place of my($foo, $bar) = @_ and does a whole lot more. method is like func but specifically for making methods. It will automatically provide the invocant as $self (by default). No more my $self = shift. It also allows signatures, very similar to Perl 6 signatures. It also does type checking, understanding all the types that Moose (or Mouse) would understand. And it does all this with no source filters. WWW: https://metacpan.org/release/Method-Signatures