use Benchmark qw( cmpthese );

cmpthese(-5, {
        deref => 'use strict; use warnings; my $x = { map { $_ => rand } 1..50 };
                  $x->{$_} = $_ for 1..100',
        none  => 'use strict; use warnings; my $x = { map { $_ => rand } 1..50 };
                  $$x{$_} = $_ for 1..100'
});

         Rate deref  none
deref 12483/s    --   -1%
none  12611/s    1%    --

         Rate  none deref
none  11938/s    --   -0%
deref 11967/s    0%    --

##</code><code>##

use Benchmark qw( cmpthese );

cmpthese(-5, {
	deref => 'use strict; use warnings;
		  srand 42;
		  my $x = { map { rand() => rand() } 1..50 };
		  srand 42;
		  $x->{rand()} = rand() for 1..100',
	none  => 'use strict; use warnings;
		  srand 42;
		  my $x = { map { rand() => rand() } 1..50 };
		  srand 42;
		  $$x{rand()} = rand() for 1..100'
});