|Function: Sends the initial status line and all headers as determined by the REPLY object *REPLY*. Returns a binary stream to which the body of the reply can be written. Once this function has been called, further changes to *REPLY* don't have any effect. Also, automatic handling of errors (i.e. sending the corresponding status code to the browser, etc.) is turned off for this request. If your handlers return the full body as a string or as an array of octets you should NOT call this function.