Project Euler 48

PE48.pl

#!/usr/bin/perl

use warnings;
use strict;
use bigint;
use List::Util qw/sum/;

my $mod = 10**10;

sub binmod{
    my ($x, $y) = @_;
    
    return 1 if $y == 0;

    my $z = &binmod($x, $y/2);

    if( $y % 2 == 0 ){
	return ($z * $z) % $mod;
    }
    else{
	return ($z * $z * $x) % $mod;
    }
}

print sum(map{ &binmod($_,$_) } 1..1000) % $mod,"\n";
# 9110846700