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. If you additionally want to process the credit card electronically,
-see Business::OnlinePayment <http://www.420.am/business-onlinepayment/>
+see Business::OnlinePayment <http://perl.business/onlinepayment>
Original author is Jon Orwant <orwant@tpj.com>, The Perl Journal and MIT
Media Lab