use strict;
use warnings;
use Time::HiRes qw(time);

# Create a large hash
my %hash;
my $count = 3_000_000;
$hash{$count} = rand(10) while $count--;

# Undefine it
print "Undefining hash.\n";
my $before = time;
undef %hash;
printf "Done in %.03f seconds\n", time - $before;