NAME
    Business::AU::ABN - Validate and format Australian Business Numbers

SYNOPSIS
      # Create a new validated ABN object
      use Business::AU::ABN;
      my $ABN = new Business::AU::ABN( '12 004 044 937' );
  
      # Validate in a single method call
      Business::AU::ABN->validate_abn( '12 004 044 937' );
  
      # Validate in a single function call
      Business::AU::ABN::validate_abn( '12 004 044 937' );
  
      # The validate_abn function is also importable
      use Business::AU::ABN 'validate_abn';
      validate_abn( '12 004 044 937' );

DESCRIPTION
    The Australian Business Number ( ABN ) is a government allocated number
    required by all businesses in order to trade in Australia. It is
    intented to provide a central, universal, and unique identifier for all
    businesses.

    It's also rather neat, in that it is capable of self-validating. Much
    like a credit card number does, a simple algorithm applied to the digits
    can confirm that the number is valid. ( Although the business may not
    actually exist ). The checksum algorithm was specifically designed to
    catch situations in which you get two digits the wrong way around, or
    something of that nature.

    "Business::AU::ABN" provides a validation/formatting mechanism, and an
    object form of an ABN number. ABNs are reformatted into the most
    preferred format, '01 234 567 890'.

    The object itself automatically stringifies to the formatted number, so
    with an object, you can safely do "print "Your ABN $ABN looks OK"" and
    other things of that nature.

  Highly flexible validation
    Apart from the algorithm itself, most of this module is aimed at making
    the validation mechanism as flexible and easy to use as possible.

    With this in mind, the "validate_abn" sub can be accessed in ANY form,
    and will just "do what you mean". See the method details for more
    information.

    Also, all validation will take just about any crap as an argument, and
    not die or throw a warning. It will just return false.

  "Group" ABNs
    The ABN supports the concept of "Groups", that is, a group of companies
    sharing a common ABN, but being seperated within it. In fact, ALL
    companies that have a regular 11 digit ABN are actually also allocated a
    group number. This group number is a 3 digit number, and are allocated
    incrementally, starting with 001. So the ABN '01 234 567 890' is
    actually also capable of being represented as '01 234 567 890 001'.

    By convention, when only a single company exists, the 001 is dropped.
    However, in common situations where an ABN value is expected, you accept
    both the 11 digit regular version, and the 14 digit group version. The
    14 digit case will also be reformatted to show the group identifier as
    an additional 3 digits group.

    Except for not allowing 000, there are no restrictions, and group
    identifiers are not included in the checksum calculation.

METHODS
  new $string
    The "new" method creates a new "Business::AU::ABN" object. Takes as
    argument a value, and validates that it is correct before creating the
    object. As such if an object is provided that passes
    "$ABN->isa('Business::AU::ABN')", it IS a valid ABN and does not need to
    be checked.

    Returns a new "Business::AU::ABN" on success, or sets the error string
    and returns false if the string is not an ABN.

  $ABN->validate_abn
    When called as a method on an object, "validate_abn" isn't really that
    useful, as ABN objects are already assumed to be correct, but the method
    is included for completeness sake.

    Returns the correctly formatted ABN (which is also 'true' in boolean
    context) if the ABN is valid, or false if not.

  Business::AU::ABN->validate_abn $string
    When called as a static method, "validate_abn" takes a string as an
    argument and attempts to validate it as an ABN.

    Returns the correctly formatted ABN (which is also 'true' in boolean
    context) if the ABN is valid. Returns false otherwise.

  Business::AU::ABN::validate_abn $string
    When called directly as a fully referenced function, "validate_abn"
    responds in exactly the same was as for the static method above.

    Returns the correctly formatted ABN (which is also 'true' in boolean
    context) if the ABN is valid. Returns false otherwise.

  validate_abn $string
    The "validate_abn" function can also be imported to your package and
    used directly, as in the following example.

      use Business::AU::ABN 'validate_abn';
      my $abn = '01 234 567 890';
      print "Your ABN is " . validate_abn($abn) ? 'valid' : 'invalid';

    The imported function reponds identically to the fully referenced
    function and the static method.

    Returns the correctly formatted ABN (which is also 'true' in boolean
    context) if the ABN is valid. Returns false otherwise.

  to_string
    The "to_string" method returns the ABN as a string. This is also the
    method called by the stringification overload.

  errstr
    When "validate_abn" or "new" return false, a message describing the
    problem can be accessed via any of the following.

      # Global variable
      $Business::AU::ABN::errstr
  
      # Class method
      Business::AU::ABN->errstr
  
      # Function
      Business::AU::ABN::errstr()

TO DO
    Add the method "ACN" to get the older Australian Company Number from the
    ABN, which is a superset of it.

SUPPORT
    Bugs should be reported via the CPAN bug tracker at

    <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Business-AU-ABN>

    For other issues, or commercial enhancement or support, contact the
    author.

AUTHORS
    Adam Kennedy <cpan@ali.as>, <http://ali.as/>

COPYRIGHT
    Copyright (c) 2003 - 2005 Adam Kennedy. All rights reserved. This
    program is free software; you can redistribute it and/or modify it under
    the same terms as Perl itself.

    The full text of the license can be found in the LICENSE file included
    with this module.

