anchor.diff:  %%%----------------------------------------------------------------------
   
   new_variable() ->
  -    [{used, Used}] = ets:lookup(?NT_USED, used),
  +    Used = get(?NT_USED),
       Fresh = erl_syntax_lib:new_variable_name(Used),
  -    ets:insert(?NT_USED, {used, sets:add_element(Fresh, Used)}),
  +    put(?NT_USED, sets:add_element(Fresh, Used)),
       erl_syntax:variable(Fresh).
   
   new_underscore_variable() ->
  -    [{used, Used}] = ets:lookup(?NT_USED, used),
  +    Used = get(?NT_USED),
       new_underscore_variable(Used).
   
   new_underscore_variable(Used) ->
  
positive.code: 
  %% Log a list of warnings, as returned by compile:file/2.
  log_warning_list(_List) -> ok.
                                                  %log_list(List, "Warning:").
  
  %% Log a list of error or warning descriptors, as returned by compile:file/2.
  log_list(List, Pre) ->
      LogFun = fun(String) -> concuerror_log:log(String) end,
      _ = [LogFun(io_lib:format("~s:~p: ~s ~s\n",
                                [File, Line, Pre, Mod:format_error(Descr)]))
           || {File, Info} <- List, {Line, Mod, Descr} <- Info],
      ok.
  
negative.code:             %% due to record expansion below.
              StrippedForms = strip_attributes(OldForms, []),
              ExpRecForms = erl_expand_records:module(StrippedForms, []),
              %% Convert `erl_parse tree` to `abstract syntax tree`.
              Tree = erl_recomment:recomment_forms(ExpRecForms, []),
              MapFun = fun(T) -> instrument_toplevel(T) end,
              Transformed = erl_syntax_lib:map_subtrees(MapFun, Tree),
              %% Return an `erl_parse-compatible` representation.
              Abstract = erl_syntax:revert(Transformed),
              ?print(Abstract),
              NewForms = erl_syntax:form_list_elements(Abstract),
  