Not optimisations, errors.

#! perl -slw
use strict;
#use sort 
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 Lice
+nse or the
   GNU General Public License, which may be found in the Perl 5 source
+ kit.
);

Benchmark::cmpthese(-1, {
   inline     => q[ sort { $a cmp $b }     @array; ],
   argless    => q[ sort argless           @array; ],
   proto      => q[ sort proto             @array; ],
   args       => q[ sort { args($a, $b) }  @array; ],
});

__END__
P:\test>410266
Possible attempt to separate words with commas at P:\test\410266.pl li
+n
Name "main::b" used only once: possible typo at P:\test\410266.pl line
Name "main::a" used only once: possible typo at P:\test\410266.pl line
Useless use of sort in void context at (eval 4) line 1.
...
Useless use of sort in void context at (eval 182) line 1.
             Rate argless   proto  inline    args
argless 6619798/s      --     -2%     -8%    -19%
proto   6748958/s      2%      --     -6%    -18%
inline  7189879/s      9%      7%      --    -12%
args    8216252/s     24%     22%     14%      --
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