$t=time; $a[ $_-123 ] = $_ for 123 .. 123+1e6; print time() - $t; print total_size \@a;;
0.252718925476074
32388792

$t=time; $h{ $_ } = $_ for 123 .. 123+1e6; print time() - $t; print total_size \%h;;
0.625
112278277