output

testing for $col_count == 1
              Rate for-each    for-c
for-each 2118644/s       --     -40%
for-c    3521127/s      66%       --
----------------------------------------
testing for $col_count == 2
              Rate for-each    for-c
for-each 1923077/s       --     -35%
for-c    2958580/s      54%       --
----------------------------------------
testing for $col_count == 4
              Rate for-each    for-c
for-each 1748252/s       --     -12%
for-c    1976285/s      13%       --
----------------------------------------
testing for $col_count == 8
              Rate    for-c for-each
for-c    1308901/s       --      -9%
for-each 1436782/s      10%       --
----------------------------------------
testing for $col_count == 16
              Rate    for-c for-each
for-c     737463/s       --     -29%
for-each 1033058/s      40%       --
----------------------------------------
testing for $col_count == 32
             Rate    for-c for-each
for-c    408163/s       --     -39%
for-each 672948/s      65%       --
----------------------------------------
testing for $col_count == 64
             Rate    for-c for-each
for-c    215332/s       --     -45%
for-each 391543/s      82%       --
----------------------------------------

test.pl

#!/usr/bin/perl

use v5.14;
use Benchmark qw(cmpthese);

for my $col_count (1, 2, 4, 8, 16, 32, 64) {
    say "testing for \$col_count == $col_count";
    cmpthese(
        5_000_000,
        {
            'for-c' => sub {
                for (my $col_index = 0 ; $col_index < $col_count ; $col_index++) {
                }
            },
            'for-each' => sub {
                for my $col_index (0 .. $col_count - 1) {
                }
            },
        });
    say '-' x 40;
}