Perl6::Subs is a source filter that adds a very useful subset of Perl
6 subroutine syntax to Perl 5.  Given a subroutine defined with a Perl
6 prototype, the code generated by Perl6::Subs will, at runtime,
declare the formal parameters, assign them their values, and validate
their contents according to both built-in and user-given rules.

WWW: https://metacpan.org/release/CHIPS/Perl6-Subs-0.05