D:\Perl\test>256024 -LEN=1000 -N=1 -CHECK

      s/iter  dio1  ari1  dio2 enlil  dio3  buk3  buk1  bu
dio1    26.1    --  -46%  -46%  -95%  -96%  -98%  -99%  -9
ari1    14.2   84%    --    0%  -90%  -92%  -97%  -98%  -9
dio2    14.2   84%    0%    --  -90%  -92%  -97%  -98%  -9
enlil   1.41 1748%  906%  906%    --  -20%  -72%  -77%  -7
dio3    1.13 2205% 1155% 1155%   25%    --  -65%  -71%  -7
buk3   0.401 6408% 3444% 3444%  252%  182%    --  -17%  -1
buk1   0.331 7785% 4193% 4193%  327%  242%   21%    --   -
buk2   0.330 7808% 4206% 4206%  328%  243%   22%    0%

Ari1:a7aab2bba7aab2bba7aab2bba7aab2bba7aab2bba7aab2bba7aab ...
buk1:a7aab2bba7aab2bba7aab2bba7aab2bba7aab2bba7aab2bba7aab ...
buk2:a7aab2bba7aab2bba7aab2bba7aab2bba7aab2bba7aab2bba7aab ... 
buk3:a7aab2bba7aab2bba7aab2bba7aab2bba7aab2bba7aab2bba7aab ... 
dio1:a7aab2bba7aab2bba7aab2bba7aab2bba7aab2bba7aab2bba7aab ...
dio2:a7aab2bba7aab2bba7aab2bba7aab2bba7aab2bba7aab2bba7aab ...
dio3:a7aab2bba7aab2bba7aab2bba7aab2bba7aab2bba7aab2bba7aab ... 
enll:a7aab2bba7aab2bba7aab2bba7aab2bba7aab2bba7aab2bba7aab ...

D:\Perl\test>256024 -LEN=1000 -N=1 -SPARSE=5 -CHECK
      s/iter   dio1   dio2   ari1  enlil   dio3   buk1   buk2   buk3
dio1     162     --   -44%   -46%   -93%   -95%  -100%  -100%  -100%
dio2    90.7    79%     --    -4%   -88%   -92%   -99%   -99%   -99%
ari1    87.5    85%     4%     --   -88%   -91%   -99%   -99%   -99%
enlil   10.6  1421%   752%   721%     --   -28%   -93%   -93%   -95%
dio3    7.67  2012%  1082%  1040%    39%     --   -90%   -90%   -94%
buk1   0.791 20376% 11364% 10956%  1246%   870%     --    -5%   -39%
buk2   0.752 21438% 11959% 11530%  1316%   920%     5%     --   -36%
buk3   0.480 33642% 18792% 18120%  2118%  1498%    65%    57%     --

Ari1:a7aab2bb....____....____....____....____....____a7aab2bb....____....
buk1:a7aab2bb....____....____....____....____....____a7aab2bb....____....
buk2:a7aab2bb....____....____....____....____....____a7aab2bb....____....
buk3:a7aab2bb....____....____....____....____....____a7aab2bb....____....
dio1:a7aab2bb....____....____....____....____....____a7aab2bb....____....
dio2:a7aab2bb....____....____....____....____....____a7aab2bb....____....
dio3:a7aab2bb....____....____....____....____....____a7aab2bb....____....
enll:a7aab2bb....____....____....____....____....____a7aab2bb....____....

D:\Perl\test>256024 -LEN=1 -N=-3
        Rate  buk3  dio3 enlil  dio2  buk2  buk1  dio1
buk3  2190/s    --   -1%   -3%   -4%  -10%  -13%  -38%
dio3  2210/s    1%    --   -2%   -3%   -9%  -13%  -37%
enlil 2259/s    3%    2%    --   -1%   -7%  -11%  -36%
dio2  2272/s    4%    3%    1%    --   -6%  -10%  -35%
buk2  2430/s   11%   10%    8%    7%    --   -4%  -31%
buk1  2527/s   15%   14%   12%   11%    4%    --  -28%
dio1  3510/s   60%   59%   55%   54%   44%   39%    --

D:\Perl\test>256024 -LEN=10 -N=-3
       Rate  dio2  dio1 enlil  dio3  buk3  buk1  buk2
dio2  177/s    --  -15%  -20%  -20%  -28%  -39%  -40%
dio1  209/s   18%    --   -5%   -5%  -15%  -28%  -29%
enlil 219/s   24%    5%    --   -0%  -10%  -25%  -26%
dio3  220/s   25%    5%    0%    --  -10%  -25%  -26%
buk3  245/s   39%   17%   12%   11%    --  -16%  -17%
buk1  292/s   65%   40%   33%   33%   19%    --   -2%
buk2  296/s   68%   42%   35%   35%   21%    2%    --

D:\Perl\test>256024 -LEN=100 -N=-3
        Rate  dio1  dio2  dio3 enlil  buk3  buk1  buk2
dio1  3.74/s    --  -36%  -84%  -84%  -85%  -87%  -87%
dio2  5.87/s   57%    --  -74%  -75%  -76%  -80%  -80%
dio3  22.8/s  510%  289%    --   -3%   -6%  -22%  -23%
enlil 23.4/s  526%  299%    3%    --   -3%  -20%  -21%
buk3  24.3/s  548%  313%    6%    3%    --  -17%  -18%
buk1  29.2/s  680%  398%   28%   25%   21%    --   -2%
buk2  29.7/s  694%  406%   30%   27%   23%    2%    --

##</code><code>##

#! perl -slw
use strict;
use vars qw[$LEN $N $SPARSE $CHECK];
use Benchmark qw[cmpthese];

our $str = '17341234';
$str .= '....____' x $SPARSE if $SPARSE;
$str x= ($LEN || 5);

our (@ari, @buk, @dio, @enlil);

my $test = {
    ari1=> q[
      $ari[1] = $str;
      local *_ = do{ \$ari[1] };
      our $i = 0;
      *_ = \substr( $ari[1], $i ) while s[(.)(...)\1(?{ $i = pos() - 4 })][a$2b];
    ],
    buk1=> q[
      $buk[1] = $str;
      substr($buk[1], $_, 5) =~ s[(.)(...)\1][a$2b] for 0 .. length ($buk[1]);
    ],
    buk2=> q[
      $buk[2] = $str;
      for( 0 .. length($buk[2]) ) { substr($buk[2], $_, 5) =~ s[(.)(...)\1][a$2b] };
    ],
    buk3=> q[
      $buk[3] =  $str;
      my $i;
      $i = pos($buk[3])-5
      , substr( $buk[3], $i, 5) =~ s[(.)(...)\1][a$2b]
      , pos($buk[3]) = $i
              while $buk[3] =~ m[(.)(...)\1]g;
    ],
    dio1=> q[
      $dio[1] = $str;
      1 while $dio[1] =~ s/(.)(...)\1/a$2b/;
    ],
    dio2=> q[
      $dio[2] = $str;
      $r = 0;
      1 while substr($dio[2],$r) =~ s/(.)(...)\1(?{$r = pos() - 3})/a$2b/;
    ],
    dio3=> q[
      $dio[3] = $str;
      $r = 0;
      1 while substr($dio[3],$r) =~ s[(.)(...)\1(?{$r +=pos() - 4})][a$2b];
    ],
    enlil=> q[{
      $enlil[1] = $str;
      our $i = 0;
      pos($enlil[1]) = $i - 4
        while $enlil[1] =~ s[\G (.*?) (.) (...) \2 (?{ $i = pos() })  ]
                            [ defined $1 ? $1.'a'.$3.'b' : 'a'.$3.'b' ]ex;
    }],
};

# A bug with Lvalue refs cause Ari1 to segfault if executed more than twice!
delete $test->{ari1}, $ari[1] = 'Test not performed'    if $N < 1 or $N > 2;

cmpthese( $N||-3, $test );

exit unless $CHECK;
print "
Ari1:$ari[1]
buk1:$buk[1]
buk2:$buk[2]
buk3:$buk[3]
dio1:$dio[1]
dio2:$dio[2]
dio3:$dio[3] 
enll:$enlil[1]
";

__END__