CheckDigits::MXX_003 - compute check digits for DEM

       Mathias Weidner, "<mamawe@cpan.org>"

ALGORITHM
       The algorithm is a variation of the Verhoeff scheme.

       0   All letters are changed to numbers.

       1   All digits are permutated according to a permutation table.

       2   The  permutated digits are combined using a dieeder table. The first with the second, the result with
           the third, this result with the fourth and so on.

       3   The result of the last combination in the dieeder table is in such a way combined that the result  is
           0 (zero). The number used for this combination is the checksum.

       For details look at the source.

   METHODS
       is_valid($number)
           Returns  true  only  if  $number consists solely of numbers and the last digit is a valid check digit
           according to the algorithm given above.

           Returns false otherwise,

       complete($number)
           The check digit for $number is computed and concatenated to the end of $number.

           Returns the complete number with check digit or '' if $number does not consist solely of  digits  and
           spaces.

       basenumber($number)
           Returns the basenumber of $number if $number has a valid check digit.

           Return '' otherwise.

       checkdigit($number)
           Returns the checkdigit of $number if $number has a valid check digit.

           Return '' otherwise.

   EXPORT
       None by default.

       CheckDigits::MXX_003 - compute check digits for DEM

       perl, CheckDigits, www.pruefziffernberechnung.de,

perl v5.36.0                                       2022-10-13               Algorithm::CheckDigits::MXX_003(3pm)

         use Algorithm::CheckDigits;

         $dem = CheckDigits('dem');

         if ($dem->is_valid('GD0645027K1')) {
               # do something
         }

         $cn = $dem->complete('GD0645027K');
         # $cn = 'GD0645027K1'

         $cd = $dem->checkdigit('GD0645027K1');
         # $cd = '1'

         $bn = $dem->basenumber('GD0645027K1');
         # $bn = 'GD0645027K'