my %data;

foreach my $x (1..5000) {
	$data{$x} = {} unless $data{$x};
	foreach my $y (1..1000) {
		$data{$x}{$y} = {} unless $data{$x}{$y};
	}
}

real	0m4.075s
user	0m3.767s
sys	0m0.289s

##</code><code>##

use threads;
use threads::shared;

my %data:shared;

foreach my $x (1..5000) {
	$data{$x} = &share( {} ) unless $data{$x};
	foreach my $y (1..1000) {
		$data{$x}{$y} = &share( {} ) unless $data{$x}{$y};
	}
}

real	1m4.984s
user	1m4.211s   ! that's ~16x times slower that the non-shared case
sys	0m0.540s