-selected. How the value from the elements is derived depends on three
-things: the parameters C<default_sub> (unset by default) and
-C<default_key> (default: "selected") as well as the element's type.
-
-=over 4
-
-=item * If C<default_sub> is a code reference then that reference is
-called with the element as its only parameter. The return value is the
-value compared to the value from the elements in C<\@collection>.
-
-=item * If the element in question is a scalar then its value is used.
-
-=item * If the element is a hash then C<default_key> names the index
-into the hash used as the value to select by default.
-
-=item * If the element is a blessed object then C<default_key> names
-the method to call on the object. That method's return value is used
-as the value to select by default.
-
-=back
-
-See the synopsis for an example using C<default> with Rose::DB::Object
-instances.