Subroutine signatures in Perl

#!/usr/bin/env perl

use v5.19.9;
use warnings;

use feature 'signatures';
no warnings 'experimental::signatures';

sub puppy_bowl ($starter, $substitute='Doodle Bug', %others) {
    say "starter = $starter";
    say "substitute = $substitute";
    say "$_ => $others{$_}" for keys %others;
}

puppy_bowl('Abdiel');
say '';
puppy_bowl('Abdiel', 'Alvin');
say '';
puppy_bowl('Abdiel', 'Alvin', backup => 'Alanis', kitty => 'Alexa');
say '';
puppy_bowl();