Rate hash   if
hash  9329/s   -- -11%
if   10473/s  12%   --

        Rate hash   if
hash  9436/s   -- -11%
if   10599/s  12%   --

        Rate hash   if
hash  9341/s   -- -12%
if   10662/s  14%   --

##</code><code>##

use strict;
use warnings;

use Benchmark qw( cmpthese );

use constant INNER => $ARGV[0] || 10000;
use constant OUTER => $ARGV[1] || -3;

my $hash = <<'__EOI__';
   use strict;
   use warnings;
   my @x = our @data;
   my %c;
   while (@x) {
      my $i = shift(@x);
      my $j = shift(@x);
      ++$c{"$i$j"};
   }
__EOI__

my $if = <<'__EOI__';
   use strict;
   use warnings;
   my @x = our @data;
   my ($c00, $c01, $c10, $c11);
   while (@x) {
      my $i = shift(@x);
      my $j = shift(@x);
      if ($i) {
         if ($j) {
            $c11++;
         } else {
            $c10++;
         }
      } else {
         if ($j) {
            $c01++;
         } else {
            $c00++;
         }
      }
   }
__EOI__

our @data = map chr('' . int(rand(2))), 1..INNER;

cmpthese(OUTER, {
   'hash' => $hash,
   'if'   => $if,
});