#!/usr/bin/perl -w
# http://c2.com/cgi/wiki?TailCallOptimization
use strict;

use Carp qw(cluck);
my $cluck = 0;

sub _f_tail_rec {
    if($_[0] == 0) {
        cluck "Goto optimized stack trace" if $cluck;
        return $_[1]
    }   
    $_[1] *= $_[0];
    $_[0]--; 
    goto &_f_tail_rec;
}   
sub f_tail_rec { @_ = (@_, 1); goto &_f_tail_rec;}

my $n = 100;
print "f_tail_rec($n) = ".f_tail_rec($n),"\n";

print "-"x20,"\n";
print "f_normal_rec($n) = ".f_normal_rec($n),"\n";

sub f_normal_rec { 
    if($_[0] == 0) {
        cluck "Recursion stack trace" if $cluck;
        return 1;
    }   
    return $_[0] * f_normal_rec($_[0]-1);
}