Your benchmark isn't comparing for-block vs map. It's comparing the for statement modifier against map. Statements modifiers don't have the overhead of entering and leaving a scope. Of course, in this particular case, the clear winner is one that doesn't loop. 
#!/usr/bin/perl

use strict;
use warnings;

use Benchmark qw /cmpthese/;

my $base = 1000;
foreach my $mult (1, 10, 100) {
    my $code;
    my $max     = $mult * $base;
    {
        no strict 'refs';
        @{"main::array$mult"} = 1 .. $max;
    }
    my $map_var = "\$sum${mult}map";
    my $for_var = "\$sum${mult}for";
    my $mod_var = "\$sum${mult}mod";
    my $exp_var = "\$sum${mult}exp";
    $code -> {"map${mult}k"} = "$map_var = 0;" .
                               "map {$map_var += \$_} \@array$mult";
    $code -> {"for${mult}k"} = "$for_var = 0;" .
                               "for (\@array$mult) {$for_var += \$_}";
    $code -> {"mod${mult}k"} = "$mod_var = 0;" .
                               "$mod_var += \$_ for \@array$mult";
    $code -> {"exp${mult}k"} = "$exp_var = $max * ($max + 1) / 2;";

    cmpthese -1 => $code;
    print "\n";
    
    no strict 'refs';
    die "Unequal\n" unless ${"sum${mult}map"} == ${"sum${mult}for"} &&
                           ${"sum${mult}mod"} == ${"sum${mult}exp"} &&
                           ${"sum${mult}map"} == ${"sum${mult}exp"};
     
}
    
__END__
           Rate   map1k   for1k   mod1k   exp1k
map1k    1305/s      --    -58%    -64%   -100%
for1k    3140/s    141%      --    -12%   -100%
mod1k    3589/s    175%     14%      --   -100%
exp1k 6859842/s 525617% 218353% 191047%      --

            Rate   map10k   for10k   mod10k   exp10k
map10k     123/s       --     -59%     -66%    -100%
for10k     299/s     144%       --     -16%    -100%
mod10k     356/s     190%      19%       --    -100%
exp10k 7021713/s 5717581% 2347785% 1970572%       --

             Rate   map100k   for100k   mod100k   exp100k
map100k    12.3/s        --      -60%      -64%     -100%
for100k    30.5/s      148%        --      -11%     -100%
mod100k    34.2/s      179%       12%        --     -100%
exp100k 5383313/s 43894609% 17663897% 15724842%        --

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Abigail

In reply to Re: When would you choose foreach instead of map? by Abigail-II
in thread When would you choose foreach instead of map? by jpfarmer

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