Um simples teste de funções com múltiplo despacho e recursão...

multi.pl

#!/home/user/localperl/bin/perl

use v5.20;
use strict;
use warnings;
use feature qw| say signatures |;

my %multi;

sub def ($name, $param, $lambda) {
	$multi{ $name } -> { $param } = \&{ $lambda }
}

sub call ($name, $arg) {
	$multi{ $name } -> { $arg } &&
		$multi{ $name } -> { $arg } -> ( ) ||
		$multi{ $name } -> { N } -> ($arg)
}

def fact =>  2  => sub      { 2 };
def fact =>  N  => sub ($N) { $N * call fact => $N - 1 };

def fib  =>  1  => sub      { 1 };
def fib  =>  2  => sub      { 1 };
def fib  =>  N  => sub ($N) { (call fib => $N - 1) + (call fib => $N - 2) };

say call fact => 5;
say call fib  => 10;

# end of script