package Thing;
    use Moose;
    use Moose::Util::TypeConstraints qw{ enum };

    has delete => (is       => 'ro',
                   isa      => enum([qw[ yes no ]]),
                   init_arg => undef,
                   lazy     => 1,
                   builder  => '_build_delete');

    has _delete => (is       => 'ro',
                    isa      => 'Bool',
                    init_arg => 'delete');

    sub _build_delete {
        my ($self) = @_;
        $self->_delete ? 'yes' : 'no'
    }