fails:Fiber.yield passes control to the Fiber's caller
fails:Fiber.yield returns to the Fiber the value of the #resume call that invoked it
fails:Fiber.yield passes control to the Fiber's caller
fails:Fiber.yield returns its arguments to the caller
fails:Fiber.yield returns to the Fiber the value of the #resume call that invoked it
fails:Fiber.yield raises a FiberError if called from the root Fiber
