anchor.diff:  			if_match(Req2, State2, ETagsList);
   		{error, badarg} ->
   			respond(Req, State2, 400)
  -	catch Class:Reason ->
  -		error_terminate(Req, State2, Class, Reason, if_match)
   	end.
   
   if_match(Req, State, EtagsList) ->
  
positive.code: 
  if_match_exists(Req, State) ->
  	State2 = State#state{exists=true},
  	try cowboy_req:parse_header(<<"if-match">>, Req) of
  		{ok, undefined, Req2} ->
  			if_unmodified_since_exists(Req2, State2);
  		{ok, '*', Req2} ->
  
negative.code: 	end.
  
  if_none_match_exists(Req, State) ->
  	case cowboy_req:parse_header(<<"if-none-match">>, Req) of
  		{ok, undefined, Req2} ->
  			if_modified_since_exists(Req2, State);
  		{ok, '*', Req2} ->
  