#!/usr/bin/perl

#sum of number between 1 and 1,000,000
$n = 1_000_000;

my $t = 0;

$t = addup( $t, $n-- ) while $n;
print "$t\n";

sub addup
{
    $_[0] + $_[1];
}

##</code><code>##

$ time ./func_tst.pl
500000500000

real    0m5.68s
user    0m5.48s
sys     0m0.02s
$ time ./loop_test.pl
500000500000

real    0m1.48s
user    0m1.47s
sys     0m0.01s