CheckDigits::M11_003 - compute check digits for PKZ (GDR)

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

ALGORITHM
       1.  The checkdigit is set to 0.

       2.  From right to left the digits are weighted (multiplied) with 2,4,8,5,10,9,7,3,6,1,2,4.

       3.  The products are added.

       4.  The sum of step 3 is taken modulo 11.

       5.  The value of step 4 is added to a multiple (0..9) of the weight of the checkdigit (2).

       6.  The sum of step 5 is taken modulo 11.

       7.  The checkdigit is the multiple of the weight of the checkdigit where the value of step 6 equals 10.

       8.  If there can't be reached a value of 10 in step 6, the number cannot be taken as a PKZ.

       To validate a PKZ apply steps 2 to 4 to the complete number.

   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::M11_003 - compute check digits for PKZ (GDR)

       perl, CheckDigits, www.pruefziffernberechnung.de.

perl v5.36.0                                       2022-10-13               Algorithm::CheckDigits::M11_003(3pm)

         use Algorithm::CheckDigits;

         $pkz = CheckDigits('pkz');

         if ($pkz->is_valid('150765400354')) {
               # do something
         }

         $cn = $pkz->complete('15076540035');
         # $cn = '150765400354'

         $cd = $pkz->checkdigit('150765400354');
         # $cd = '4'

         $bn = $pkz->basenumber('150765400354');
         # $bn = '150765400354'