anchor.diff:        next(Req2, State2, fun send_req_headers/2)
     end.
   
  -send_req_headers(Req, State=#state{conn=Conn, req_headers=ReqHeaders, backend=Backend}) ->
  +send_req_headers(Req, State=#state{req_headers=ReqHeaders, backend=Backend}) ->
     FormattedHeaders = [case Name of
       <<"host">> ->
         format_header(Name, format_host_header(Backend));
  
positive.code:   conn :: any(),
    backend :: {atom(), list(), integer(), binary()},
    timeout :: integer(),
    req_headers :: binary()
  }).
  
  -define(DEFAULT_TIMEOUT, 5000).
  
negative.code:       next(Req, State, 502)
    end.
  
  init_request(Req, State=#state{method=Method}) ->
    {Path, Req2} = cowboy_req:path_info(Req),
    {Version, Req3} = cowboy_req:version(Req2),
    Message = format_request(Method, Path, Version),
    send(Req3, State, Message, fun forwarded_header_prefix/2).
  
  forwarded_header_prefix(Req, State=#state{backend=Backend, req_headers=ReqHeaders}) ->
    case call(Req, State, forwarded_header_prefix) of
  