purple:/tmp oneiros$ perl -version | head -2

This is perl, v5.8.6 built for darwin-thread-multi-2level
purple:/tmp oneiros$ perl timer.pl

100:
           Rate      map  new_map void_map      for  foreach
map      1089/s       --     -16%     -37%     -61%     -61%
new_map  1295/s      19%       --     -25%     -54%     -54%
void_map 1718/s      58%      33%       --     -38%     -39%
for      2793/s     156%     116%      63%       --      -1%
foreach  2825/s     159%     118%      64%       1%       --

500:
          Rate      map  new_map void_map  foreach      for
map      213/s       --     -14%     -35%     -60%     -60%
new_map  249/s      17%       --     -24%     -53%     -54%
void_map 328/s      54%      32%       --     -38%     -39%
foreach  526/s     147%     112%      61%       --      -2%
for      538/s     153%     116%      64%       2%       --

2500:
            Rate      map  new_map void_map      for  foreach
map       38.5/s       --     -15%     -38%     -61%     -61%
new_map   45.4/s      18%       --     -27%     -54%     -55%
void_map  61.9/s      61%      37%       --     -38%     -38%
for       99.5/s     158%     119%      61%       --      -0%
foreach  100.0/s     160%     120%      61%       0%       --

##</code><code>##

use warnings;
use strict;

use Benchmark qw(cmpthese);

my @counts = qw( 100 500 2500 );
my %templates = (
        map      => '@list = map { s/1//; $_ } @list;',
        new_map  => 'my @newlist = map { s/1//; $_ } @list;',
        void_map => 'map { s/1// } @list;',
        foreach  => 's/1// foreach @list;',
        for      => 's/1// for @list;'
);

my @tests = ();
while ( my ($name, $template) = each (%templates)) {
        my $test = <<EOF;
\$test = sub {
        my \@list = \@_;
        $template
}
EOF
        eval $test;
        foreach my $count (@counts) {
                $tests[$count]->{$name} = sub { &$test( 1 .. $count ) };
        }
}

foreach my $count (@counts) {
        print "\n$count:\n";
        cmpthese( 500_000/$count, $tests[$count] );
}