Instead of $self->get_param( 'breadcrumb' ), try $self->get_breadcrumb().

Consider how they would each act if you misspell "breadcrumb" as "braedcrumb". $self->get_param( 'braedcrumb' ) will silently return false and you'll spend half an hour trying to figure out why the site's breadcrumb links aren't displaying correctly, but $self->get_braedcrumb() will give you an instant "that method doesn't exist" error.