use warnings;
use strict;

use Benchmark;
my $start = new Benchmark;

my $size = 10000000;
my %hash;
keys(%hash) = $size;

for my $i (1..$size) {
    my $key = "key$i";
    $hash{$key} = $key;
}

my $end = new Benchmark;
my $diff = timediff ($end, $start);
print "The code ran for \n",timestr($diff),"\n";

##</code><code>##

19 wallclock secs (17.36 usr +  0.94 sys = 18.30 CPU)

##</code><code>##

21 wallclock secs (21.23 usr +  0.63 sys = 21.86 CPU)