my ($this, $a, $b) = @_;

##</code><code>##

sub convert (:$from, :$to, :$thing) { ... }

##</code><code>##

package Signatures;

sub import {
	no warnings;
	no strict;
	my $package = caller;
	for (keys %{ $package . '::' }) {
		next unless exists &{ $package . "::$_" };
		my $sub = \ &{ $package . "::$_" };
		next unless my $proto = prototype $sub;
		*{ $package . "::$_" } = eval qq {
			sub { 
				package $package; 
				local ($proto) = \@_; 
				\$sub->() 
			}
		}
	}
}

##</code><code>##

#!perl -l

foo("aaaa", "bbb");

sub foo ($a, $b) { print $a; print $b }

use Signatures;