anchor.diff:  
   -spec qs_val(Name::string(), Req::#http_req{})
   	-> {Value::string() | true | undefined, Req::#http_req{}}.
  -qs_val(Name, Req=#http_req{raw_qs=RawQs, qs_vals=undefined}) ->
  -	QsVals = parse_qs(RawQs),
  -	qs_val(Name, Req#http_req{qs_vals=QsVals});
  +%% @equiv qs_val(Name, Req) -> qs_val(Name, undefined, Req)
   qs_val(Name, Req) ->
  -	case lists:keyfind(Name, 1, Req#http_req.qs_vals) of
  -		{Name, Value} -> {Value, Req};
  -		false -> {undefined, Req}
  -	end.
  -
  --spec qs_val(Name::string(), Default::term(), Req::#http_req{})
  -	-> {Value::string() | term() | true, Req::#http_req{}}.
  +	qs_val(Name, undefined, Req).
  +
  +-spec qs_val(Name::string(), Default, Req::#http_req{})
  +	-> {Value::string() | true | Default, Req::#http_req{}}
  +	when Default::term().
   qs_val(Name, Default, Req=#http_req{raw_qs=RawQs, qs_vals=undefined}) ->
   	QsVals = parse_qs(RawQs),
   	qs_val(Name, Default, Req#http_req{qs_vals=QsVals});
   qs_val(Name, Default, Req) ->
  -	Value = proplists:get_value(Name, Req#http_req.qs_vals, Default),
  -	{Value, Req}.
  +	case lists:keyfind(Name, 1, Req#http_req.qs_vals) of
  +		{Name, Value} -> {Value, Req};
  +		false -> {Default, Req}
  +	end.
   
   -spec qs_vals(Req::#http_req{})
   	-> {list({Name::string(), Value::string() | true}), Req::#http_req{}}.
  
positive.code: %% Copyright (c) 2011, Loïc Hoguin <essen@dev-extend.eu>
  %%
  %% Permission to use, copy, modify, and/or distribute this software for any
  %% purpose with or without fee is hereby granted, provided that the above
  
negative.code: 
  -spec header(Name::atom() | string(), Req::#http_req{})
  	-> {Value::string() | undefined, Req::#http_req{}}.
  %% @equiv header(Name, Req) -> header(Name, undefined, Req)
  header(Name, Req) ->
  	header(Name, undefined, Req).
  
  -spec header(Name::atom() | string(), Default, Req::#http_req{})
  	-> {Value::string() | Default, Req::#http_req{}} when Default::term().
  header(Name, Default, Req) ->
  	case lists:keyfind(Name, 1, Req#http_req.headers) of
  		{Name, Value} -> {Value, Req};
  		false -> {Default, Req}
  	end.
  
  -spec headers(Req::#http_req{})
  	-> {list({Name::atom() | string(), Value::string()}), Req::#http_req{}}.
  