CheckDigits::M09_001 - compute check digits for Euro notes

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

ALGORITHM
       1.  Letters are replaced with their position in the alphabet ('A' = 1, ...).

       2.  The total of the digits of all numbers is computed.

       3.  This sum is taken modulo 9.

       4.  The check digit is the difference between 8 and the number of step 3.

       To validate the last digit of the total of the digits of all numbers inclusive check digit must be 8.

   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.

       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::M09_001 - compute check digits for Euro notes

       perl, CheckDigits, www.pruefziffernberechnung.de.

perl v5.36.0                                       2022-10-13               Algorithm::CheckDigits::M09_001(3pm)

         use Algorithm::CheckDigits;

         $euro = CheckDigits('euronote');

         if ($euro->is_valid('X07738250357')) {
               # do something
         }

         $cn = $euro->complete('X0773825035');     # $cn = 'X07738250357'

         $cd = $euro->checkdigit('X07738250357'); # $cd = '7'

         $bn = $euro->basenumber('X07738250357'); # $bn = 'X0773825035'