CheckDigits::M11_007 - compute check digits for VAT Registration Number (FI)

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

ALGORITHM
       1.  Beginning left every digit is weighted with 7,9,10,5,8,4,2.

       2.  The weighted digits are added.

       3.  The sum from step 2 is taken modulo 11.

       4.  The  checkdigit  is 11 minus the sum from step 3. Is the difference 10, the number won't be taken. If
           the difference is 11, the checkdigit is 0.

   METHODS
       is_valid($number)
           Returns true only if $number consists solely of digits and the rightmost 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 appended to the end of $number.

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

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

           Return '' otherwise.

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

           Return '' otherwise.

   EXPORT
       None by default.

       CheckDigits::M11_007 - compute check digits for VAT Registration Number (FI)

       perl, CheckDigits, http://www.pruefziffernberechnung.de/U/USt-IdNr.shtml#PZFI (german)

perl v5.36.0                                       2022-10-13               Algorithm::CheckDigits::M11_007(3pm)

         use Algorithm::CheckDigits;

         $ustid = CheckDigits('ustid_fi');

         if ($ustid->is_valid('13669598')) {
               # do something
         }

         $cn = $ustid->complete('1366959');
         # $cn = '13669598'

         $cd = $ustid->checkdigit('13669598');
         # $cd = '8'

         $bn = $ustid->basenumber('13669598');
         # $bn = '1366959';