$a[ $_*2 ] = $_ for 1 .. 1e5;;
$h{ $_*2 } = $_ for 1 .. 1e5;;

print total_size( $_ ) for \( @a, %h );;
4497312
7393098

undef( @a ); undef( %h );;
$a[ $_*20 ] = $_ for 1 .. 1e5;;
$h{ $_*20 } = $_ for 1 .. 1e5;;

print total_size( $_ ) for \( @a, %h );;
19177376
7493098

undef( @a ); undef( %h );;
$a[ $_*50 ] = $_ for 1 .. 1e5;;
$h{ $_*50 } = $_ for 1 .. 1e5;;

print total_size( $_ ) for \( @a, %h );;
69509024
7526431

##</code><code>##

$a[ $_ * 20 ] = $_ for 1 .. 1e5;;

$found = 0; say time; defined( $a[ $_ ] ) and ++$found for 1 .. 20e5; say time; say $found;;
1359141040.60138
1359141041.00958
100000

$h{ $_ * 20 } = $_ for 1 .. 1e5;;

$found = 0; say time; exists( $h{ $_ } ) and ++$found for 1 .. 20e5; say time; say $found;;
1359141122.04252
1359141123.06596
100000