subtype 'cf_class',
			 => as 'Str',
			 => where { m/a-zA-Z0-9/ },
			 => message { 'Not a valid cf class' };
	  has 'class' => {
			 is => 'rw',
			 isa => 'cf_class'
	  };

##</code><code>##

Usage: has 'name' => ( key => value, ... ) at /home/neil/perl5/lib/perl5/x86_64-linux-thread-multi/Moose.pm line 74.
        Moose::has('Moose::Meta::Class=HASH(0x2b9fe98)', 'class', 'HASH(0x2a9ef98)') called at /home/neil/perl5/lib/perl5/x86_64-linux-thread-multi/Moose/Exporter.pm line 382