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.

The validate() subroutine returns 1 if the card number provided passes
the checksum test, and 0 otherwise.

The cardtype() subroutine returns a string containing the type of card:
"MasterCard", "VISA", and so on.  My list is not complete; I welcome
additions.

The generate_last_digit() subroutine computes and returns the last digit
of the card given the preceding digits.  With a 16-digit card, you
provide the first 15 digits; the subroutine returns the sixteenth.

WWW: http://search.cpan.org/search?dist=Business-CreditCard