CheckDigits::M11_002 - compute check digits for PZN (DE)

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

ALGORITHM
       1.  From left to right beginning with the first position all digits are multiplied with 2,3,4,...

       2.  The sum of all products is computed.

       3.  The checkdigit ist the sum of step 2 taken modulo 11.

       4.  If the checkdigit is '10' the whole number is not taken as a PZN.

   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_002 - compute check digits for PZN (DE)

       perl, CheckDigits, www.pruefziffernberechnung.de.

perl v5.36.0                                       2022-10-13               Algorithm::CheckDigits::M11_002(3pm)

         use Algorithm::CheckDigits;

         $pzn = CheckDigits('pzn');

         if ($pzn->is_valid('4877800')) {
               # do something
         }

         $cn = $pzn->complete('487780');
         # $cn = '4877800'

         $cd = $pzn->checkdigit('4877800');
         # $cd = '0'

         $bn = $pzn->basenumber('4877800');
         # $bn = '487780'