use strict;
use warnings;
use Benchmark qw(cmpthese);

for my $size (5,50,500) {
  my @lol  = map { [$_, qw(some random useless data)] } (1..$size);
  print "\n\nComparing 'map' and 'for' hash-assignment from array of $size elements\n";
  cmpthese (-2, {
    for => sub { my %hash; $hash{$_->[0]} = $_ for @lol;  },
    map => sub { my %hash; %hash = map{$_->[0] => $_} @lol;  } 
  });
}

## OUTPUTS ##

Comparing 'map' and 'for' hash-assignment from array of 5 elements
Benchmark: running for, map, each for at least 2 CPU seconds...
       for:  3 wallclock secs ( 2.22 usr +  0.00 sys =  2.22 CPU) @ 77311.15/s (n=171940)
       map:  1 wallclock secs ( 2.19 usr +  0.00 sys =  2.19 CPU) @ 55606.20/s (n=122000)
       Rate  map  for
map 55606/s   -- -28%
for 77311/s  39%   --


Comparing 'map' and 'for' hash-assignment from array of 50 elements
Benchmark: running for, map, each for at least 2 CPU seconds...
       for:  2 wallclock secs ( 2.04 usr +  0.00 sys =  2.04 CPU) @ 9992.17/s (n=20414)
       map:  2 wallclock secs ( 2.12 usr +  0.00 sys =  2.12 CPU) @ 5657.09/s (n=12010)
      Rate  map  for
map 5657/s   -- -43%
for 9992/s  77%   --


Comparing 'map' and 'for' hash-assignment from array of 500 elements
Benchmark: running for, map, each for at least 2 CPU seconds...
       for:  3 wallclock secs ( 2.01 usr +  0.00 sys =  2.01 CPU) @ 948.83/s (n=1910)
       map:  2 wallclock secs ( 2.07 usr +  0.00 sys =  2.07 CPU) @ 335.75/s (n=696)
     Rate  map  for
map 336/s   -- -65%
for 949/s 183%   --