PURPOSE
Check that the required (!) postfix sigil works, and that the scalar (($), array (@) and hash (%) prefix sigils work.
Check that the + postfix sigil works, that numbers can default to values other than zero, and that an explicit isa works.
Make sure that sigils are just hints, and can be overridden by an explicit attribute spec.
Checks that attribute specs can be hashrefs or arrayrefs.
AUTHOR
Toby Inkster <tobyink@cpan.org>.
COPYRIGHT AND LICENCE
This software is copyright (c) 2012 by Toby Inkster.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.