anchor.diff:  pattern_for_cowboy(_Error) ->
       error.
   
  --type fill_pattern_t() :: 'undefined' | {binary(), [{integer(), integer()}]}.
  +-type fill_pattern_t() :: {binary(), [{integer(), integer()}]}.
   -spec prepare_filling('undefined' | binary() | [binary()]) -> fill_pattern_t() | [fill_pattern_t()].
   prepare_filling(List) when is_list(List) ->
       lists:map(
           fun(Item) -> prepare_filling(Item) end, List);
   prepare_filling(undefined) ->
  -    undefined;
  +    ?EMPTY_PATTERN;
   prepare_filling(Pattern) ->
       case re:run(Pattern, "{[^}]+}", [global]) of
           {match, Match} ->
  
positive.code:     undefined.
  
  prepare_matching(undefined) ->
      undefined;
  prepare_matching(Pattern) ->
      EPattern0 = binary:replace(Pattern, <<".">>, <<"\\">>, [global, {insert_replaced, 1}]),
      EPattern = binary:replace(EPattern0, <<"#">>, <<".*">>, [global]),
  
negative.code: 
  pattern_test_()-> [
      matchtst(#{}, <<"normal/uri">>, <<"normal/uri">>),
      matchtst(#{}, <<>>, <<>>),
      matchtst(undefined, <<>>, <<"any/uri">>),
      matchtst(undefined, <<"normal/uri">>, <<"another/uri">>),
      matchtst(#{devaddr => <<"00112233">>}, <<"{devaddr}">>, <<"00112233">>),
      matchtst(#{devaddr => <<"00112233">>}, <<"prefix.{devaddr}">>, <<"prefix.00112233">>),
  