Business::CreditCard These subroutines tell you whether a credit card number is self-consistent -- whether the last digit of the number is a valid checksum for the preceding digits. Jon Orwant The Perl Journal and MIT Media Lab orwant@tpj.com Current maintainer is Ivan Kohler . Please don't bother Jon with emails about this module. Lee Lawrence and Neale Banks contributed support for additional card types. Lee also contributed a working test.pl.