use Benchmark qw/cmpthese/;
my $lim = 1000;
our($SUM1, $SUM2);
my($sum1, $sum2);

cmpthese(-3,{
    'for'     => sub{$sum1 = 0; for(my $i = 1; $i <= $lim; $i++){$sum1+=$i}},
    'FOR'     => sub{$SUM1 = 0; for(my $i = 1; $i <= $lim; $i++){$SUM1+=$i}},
    'foreach' => sub{$sum2 = 0; for my $i (1 .. $lim){$sum2+=$i}},
    'FOREACH' => sub{$SUM2 = 0; for my $i (1 .. $lim){$SUM2+=$i}},
});
__END__

OUTPUT: with absolute rates removed:

with $lim = 10:
                 FOR FOREACH foreach     for
    FOR           --    -15%    -16%    -34%
    FOREACH      18%      --     -0%    -22%
    foreach      18%      0%      --    -22%
    for          51%     28%     27%      --


with $lim = 1000:
                 FOR     for FOREACH foreach
    FOR           --    -42%    -44%    -46%
    for          73%      --     -3%     -6%
    FOREACH      78%      3%      --     -4%
    foreach      84%      7%      4%      --