Perl Benchmark Keys on Hash

benchmark_keys.pl

#!/usr/bin/perl

use strict;
use warnings;

use Benchmark;

print "Perl version $]\n";

my %subs;
for my $n (1 .. 5) {
    my $m = 10 ** $n;
    keys(my %h) = $m; #preallocated the hash so it doesn't have to keep growing
    my $k = "a";
    %h = ( map { $k++ => 1 } 1 .. $m );
    $subs{"10^$n keys"} = sub {
        return scalar(keys %h);
    }
};

Benchmark::cmpthese -1, \%subs;