C:\test>p1
$t = time; my %h; keys %h = 10e6; $h{$_}=1 for 1 .. 10e6; printf "%.6f\n", time() -$t;;
15.792654

$t = time; my %i; $i{$_}=1 for 1 .. 10e6; printf "%.6f\n", time() -$t;;
18.772236