This module calculates the Modulus 10 Double Add Double checksum, also known as the LUHN Formula. This algorithm is used to verify credit card numbers and Standard & Poor's security identifiers such as CUSIP and CSIN. You can find plenty of information about the algorithm by searching the web for "modulus 10 double add double". WWW: http://search.cpan.org/dist/Algorithm-LUHN/ - Aaron Dalton aaron@daltons.ca