use Benchmark ();

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

my @array = 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 { $a cmp $b }     @array; },
   argless    => sub { my @sorted = sort argless           @array; },
   proto      => sub { my @sorted = sort proto             @array; },
   args       => sub { my @sorted = sort { args($a, $b) }  @array; },
});

__END__
           Rate    args   proto argless  inline
args     4634/s      --    -57%    -63%    -81%
proto   10735/s    132%      --    -14%    -57%
argless 12462/s    169%     16%      --    -50%
inline  24920/s    438%    132%    100%      --