sub skeeve2 {
   my %count;

   for my $i (0..length($seq)-GROUP_LENGTH) {
      $count{substr($seq, $i, GROUP_LENGTH)}++;
   }

   my @keys = keys %count;
   foreach my $key (@keys) {
      for my $i (1..GROUP_LENGTH-1) {
         $count{substr($key, 0, $i)} += $count{$key};
      }
   }
   for my $i (1..GROUP_LENGTH-1) {
      for my $j ($i..GROUP_LENGTH-1) {
	      ++$count{substr($seq, -$j, $i)};
	  }
   }
   1;
}


sub skeeve3 {
   my %count;

   $count{"$1$2"}++ while $seq =~ /(.)(?=(..))/g;

   my @keys = keys %count;
   foreach my $key (@keys) {
      for my $i (1..GROUP_LENGTH-1) {
         $count{substr($key, 0, $i)} += $count{$key};
      }
   }
   for my $i (1..GROUP_LENGTH-1) {
      for my $j ($i..GROUP_LENGTH-1) {
	      ++$count{substr($seq, -$j, $i)};
	  }
   }

   1;
}


sub skeeve3_i {
   my %count;

   $count{$1}++ while $seq =~ /(?=(.{3}))/g;

   my @keys = keys %count;
   foreach my $key (@keys) {
      for my $i (1..GROUP_LENGTH-1) {
         $count{substr($key, 0, $i)} += $count{$key};
      }
   }
   for my $i (1..GROUP_LENGTH-1) {
      for my $j ($i..GROUP_LENGTH-1) {
	      ++$count{substr($seq, -$j, $i)};
	  }
   }

   1;
}