Business::ISIN - validate International Securities Identification Numbers

       Thanks to Peter Dintelmann (Peter.Dintelmann@Dresdner-Bank.com) and Tim Ayers (tim.ayers@reuters.com) for
       suggestions and help debugging this module.

       David Chan <david@sheetmusic.org.uk>

       Copyright  (C) 2002, David Chan. All rights reserved. This program is free software; you can redistribute
       it and/or modify it under the same terms as Perl itself.

perl v5.36.0                                       2022-11-21                                          ISIN(3pm)

       "Business::ISIN" is a class which validates ISINs (International Securities Identification Numbers), the
       codes which identify shares in much the same way as ISBNs identify books.  An ISIN consists of two
       letters, identifying the country of origin of the security according to ISO 3166, followed by nine
       characters in [A-Z0-9], followed by a decimal check digit.

       The "new()" method constructs a new ISIN object.  If you give it a scalar argument, it will use the
       argument to initialize the object's value.  Here, no attempt will be made to check that the argument is
       valid.

       The "set()" method sets the ISIN's value to a scalar argument which you give.  Here, no attempt will be
       made to check that the argument is valid.  The method returns the object, to allow you to do things like
       "$isin->set("GB0004005475")->is_valid".

       The "get()" method returns a string, which will be the ISIN's value if it is syntactically valid, and
       undef otherwise.  Interpolating the object reference in double quotes has the same effect (see the
       synopsis).

       The "is_valid()" method returns true if the object contains a syntactically valid ISIN.  (Note: this does
       not guarantee that a security actually exists which has that ISIN.) It will return false otherwise.

       If an object does contain an invalid ISIN, then the "error()" method will return a string explaining what
       is wrong, like any of the following:

       •   'xxx' does not start with a 2-letter country code

       •   'xxx' does not have characters 3-11 in [A-Za-z0-9]

       •   'xxx' character 12 should be a digit

       •   'xxx' has too many characters

       •   'xxx' has an inconsistent check digit

       Otherwise, "error()" will return "undef".

       "check_digit()"  is an ordinary subroutine and not a class method.  It takes a string of the first eleven
       characters of an ISIN as an argument (e.g.  "US459056DG9"), and returns the  corresponding  check  digit,
       calculated using the so-called 'double-add-double' algorithm.

       "check_digit()" will croak with the message 'Invalid data' if you pass it an unsuitable argument.

       Business::ISIN - validate International Securities Identification Numbers

       Perl5, Locale::Country, Carp

           use Business::ISIN;

           my $isin = new Business::ISIN 'US459056DG91';

           if ( $isin->is_valid ) {
               print "$isin is valid!\n";
               # or: print $isin->get() . " is valid!\n";
           } else {
               print "Invalid ISIN: " . $isin->error() . "\n";
               print "The check digit I was expecting is ";
               print Business::ISIN::check_digit('US459056DG9') . "\n";
           }

       0.20