use Benchmark  qw( cmpthese );
use List::Util qw( shuffle );

my @set = shuffle 1 .. 1_000_000;

cmpthese( 100,
          { 'sort' => sub { my @x = sort { $b <=> $a } @set; return; },
            'rsort' => sub { my @x = reverse sort { $a <=> $b } @set; return; },
       } );
__END__
        Rate  sort rsort
sort  1.01/s    --   -2%
rsort 1.03/s    2%    --