Your Foreach test uses map, and your Map test uses foreach. You're making me dizzy. After fixing the test names and running the test for 10 seconds, foreach was 76% faster than map:

          Rate     Map Foreach
Map     21.9/s      --    -43%
Foreach 38.6/s     76%      --

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Foreach is faster as expected, since foreach doesn't have to build a long list like map does. Update: I wrote a foreach loop that builds an array which is later assigned to %hash. As you can see below, "Map" and "Map-like" have very similar results, as expected.

use strict;

use Benchmark ();

Benchmark::cmpthese(-10, {
   "Map"      => sub { my %hash = map{$_=>1} (1..10000); },
   "Foreach"  => sub { my %hash; $hash{$_} = 1 foreach (1..10000); },
   "Map-like" => sub { my @a; push(@a, $_, 1) foreach (1..10000);
                       my %hash = @a; },
})


__END__
           Rate Map-like      Map  Foreach
Map-like 21.5/s       --      -1%     -44%
Map      21.8/s       1%       --     -43%
Foreach  38.6/s      80%      77%       --

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In reply to Re: performance of map vs. foreach by ikegami
in thread performance of map vs. foreach by johnnywang

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