as the L<Moose::Meta::Attribute> object for the attribute. The trigger
is called I<after> the value is set.
+This differs from an after method modifier in two ways. First, a
+trigger is only called when the attribute is set, as opposed to
+whenever the accessor is called. Second, it is also called if the
+attribute is set via a lazy default or builder.
+
=head2 Attribute Types
Attributes can be restricted to only accept certain types: