use Benchmark ();

sub argless   { $hash{$a   } cmp $hash{$b   } }
sub proto($$) { $hash{$_[0]} cmp $hash{$_[1]} }
sub args      { $hash{$_[0]} cmp $hash{$_[1]} }

our %hash = map { (''.rand()) => $_ } qw(
   Perl may be copied only under the terms of either the Artistic License or the
   GNU General Public License, which may be found in the Perl 5 source kit.
);

Benchmark::cmpthese(0, {
   inline     => sub { my @sorted = sort { $hash{$a} cmp $hash{$b} } keys %hash; },
   argless    => sub { my @sorted = sort argless                     keys %hash; },
   proto      => sub { my @sorted = sort proto                       keys %hash; },
   args       => sub { my @sorted = sort { args($a, $b) }            keys %hash; },
});

__END__
          Rate    args   proto argless  inline
args    2832/s      --    -33%    -42%    -43%
proto   4258/s     50%      --    -13%    -14%
argless 4871/s     72%     14%      --     -2%
inline  4973/s     76%     17%      2%      --