Route prefix doesn't work after route creation, or in mvc routes or while importing an existing app

Foo {
  get("/route", req-> req.route().name())
     .name("foo")
}
{
  use(new Foo("bar"));
}

A call to /route must display /bar/foo not /foo

dynamic route documentation is available here: http://jooby.org/doc/#routes-dynamic-advanced-routing