#!/usr/bin/perl

use strict;
use warnings;

use Benchmark qw /timethese cmpthese/;

our ($x, $y);
our  $N = shift || 100;

cmpthese -1  => {
    noduff   => '$x = 0;
                 my $n = $N;
                 while ($n --) {$x ++}',
    duff     => '$y = 0;
                 my $n = int (($N + 7) / 8);
                 goto "LABEL" . ($N % 8);
                 {   LABEL0: $y ++;
                     LABEL7: $y ++;
                     LABEL6: $y ++;
                     LABEL5: $y ++;
                     LABEL4: $y ++;
                     LABEL3: $y ++;
                     LABEL2: $y ++;
                     LABEL1: $y ++;
                     redo if -- $n > 0
                  }',
};

die "Unequal \$N == $N; \$x == $x; \$y == $y.\n" unless $N == $x && $N == $y;

__END__
          Rate noduff   duff
noduff 39384/s     --   -42%
duff   68267/s    73%     --