use Benchmark 'cmpthese';
use strict;
my $x = 0; our $y = \$x;
cmpthese( 10000000, {
    'braces'   => sub { return ${ $y } },
    'nobraces' => sub { return $$y },
});

##</code><code>##

Benchmark: timing 10000000 iterations of braces, nobraces...
    braces:  2 wallclock secs ( 1.87 usr +  0.00 sys =  1.87 CPU) @ 5347593.58/s (n=10000000)
  nobraces:  1 wallclock secs ( 1.87 usr +  0.00 sys =  1.87 CPU) @ 5347593.58/s (n=10000000)
              Rate nobraces   braces
nobraces 5347594/s       --       0%
braces   5347594/s       0%       --

##</code><code>##

my $x = [ [ 1, 2 ], [ 3, 4 ] ];
my @y = @$x->[ 0 ];
my @z = @{ $x->[ 0 ] };