anchor.diff:  %% Argument
   %%------------------------------------------------------------------------------
   
  +-spec read_arg(state()) -> state().
   read_arg(#{src := <<"%"/utf8, Src/binary>>} = State) ->
     case erlang:get(arg_env) of
       undefined ->
  
positive.code: %% #() fn
  %%------------------------------------------------------------------------------
  
  read_fn(#{loc := Loc} = State) ->
    case erlang:get(arg_env) of
      undefined -> ok;
  
negative.code: %% Unquote
  %%------------------------------------------------------------------------------
  
  -spec read_unquote(state()) -> state().
  read_unquote(#{src := <<"~"/utf8, Src/binary>>} = State) ->
    case Src of
      <<"@", _/binary>> ->
  