Business::creditcard 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.

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.