Version 1.11
  03/25/02 - Fixed error method to jive with with documentation by returning
    "undef" when the CINS was valid.

    Reset $ERROR to undef when is_valid is called and there is no problem.

Version 1.10
  03/12/02 - Completely fixed this module. It was horribly broken and couldn't
    have validated a true CINS if its life depended on it.

Version 1.00
  11/18/01 - Added the error() method.

Version 0.03
  5/9/01 - Added t/06-acc.t test.

  5/8/01 - Fixed documentation typo.