Version 1.00
11/18/01 - Added the error() method.
Version 0.03
05/09/01 - Added t/05-acc.t test.
Version 0.02
05/03/01 - Added a lot of validations in is_valid. Added new test t/04-bad.t
to check new validations.
05/01/01 - Changed the way the list of A..Z valid_chars is generated to be
more explicit.