#! perl
use strict;
use warnings;
use Benchmark qw( cmpthese );

my $n                  = 1e6;
my $foreach_loop_total =   0;
my $c_for_loop_total   =   0;

cmpthese
(
    1000,
    {
        foreach_loop => \&foreach_loop,
        c_for_loop   => \&c_for_loop,
    }
);

print "\$foreach_loop_total = $foreach_loop_total\n";
print "\$c_for_loop_total   = $c_for_loop_total\n";

sub foreach_loop
{
    $foreach_loop_total += -$_ for -$n .. 0;
}

sub c_for_loop
{
    for (my $j = $n; $j >= 0; --$j)
    {
        $c_for_loop_total += $j;
    }
}

##</code><code>##

12:00 >perl 555_SoPW.pl
               Rate foreach_loop   c_for_loop
foreach_loop 5.62/s           --          -8%
c_for_loop   6.13/s           9%           --
$foreach_loop_total = 500000500000000
$c_for_loop_total   = 500000500000000

12:05 >