Perl Benchmark on Keys (with a wrapper function)

benchmark_keys.pl

#!/opt/perl/bin/perl

use strict;
use warnings;

use Benchmark;

# Perl version 5.010001
#                Rate 10^4 keys 10^3 keys 10^5 keys 10^1 keys 10^2 keys
# 10^4 keys 2429401/s        --       -0%       -1%       -2%       -2%
# 10^3 keys 2429401/s        0%        --       -1%       -2%       -2%
# 10^5 keys 2453219/s        1%        1%        --       -1%       -1%
# 10^1 keys 2477508/s        2%        2%        1%        --       -1%
# 10^2 keys 2490475/s        3%        3%        2%        1%        --

print "Perl version $]\n";

my %subs;

sub getKeys {
    my $hh = shift;
    return keys(%$hh);
}

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);
        return scalar(getKeys(\%h));
    }
};

Benchmark::cmpthese -1, \%subs;