since has foo => (isa => subtype 'Int', where { $_ > 0 }, is => 'ro');
doesn't really work as might be expected
has 'size' => (
is => 'ro',
- isa => subtype 'Int' => where { $_ > 0 },
+ isa => subtype('Int' => where { $_ > 0 }),
);
This is handy when you want to create a one-off type and don't want to