anchor.diff:  
   %% Log a list of warnings, as returned by compile:file/2.
   log_warning_list(_List) -> ok.
  -                                                %log_list(List, "Warning:").
  +    %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],
  +    Strings = [io_lib:format("~s:~p: ~s ~s\n",
  +                    [File, Line, Pre, Mod:format_error(Descr)])
  +              || {File, Info} <- List, {Line, Mod, Descr} <- Info],
  +    concuerror_log:log(lists:flatten(Strings)),
       ok.
  
positive.code:         {ok, Module, Warnings} ->
              %% Log warning messages.
              log_warning_list(Warnings),
              %% A table for holding used variable names.
              ?NT_USED = ets:new(?NT_USED, [named_table, private]),
              %% Instrument given source file.
              concuerror_log:log("Instrumenting file ~p...~n", [File]),
              case instrument(File, Includes, Defines) of
                  {ok, NewForms} ->
                      %% Delete `used` table.
                      ets:delete(?NT_USED),
                      %% Compile instrumented code.
                      %% TODO: More compile options?
                      concuerror_log:log("Compiling instrumented code...~n"),
                      CompOptions = [binary],
                      case compile:forms(NewForms, CompOptions) of
                          {ok, Module, Binary} -> {Module, File, Binary};
                          error -> concuerror_log:log("error~n"), error
                      end;
                  {error, Error} ->
                      concuerror_log:log("error: ~p~n", [Error]),
                      %% Delete `used` table.
                      ets:delete(?NT_USED),
                      error
              end;
          {error, Errors, Warnings} ->
  
negative.code: %%%----------------------------------------------------------------------
  
  new_variable() ->
      Used = get(?NT_USED),
      Fresh = erl_syntax_lib:new_variable_name(Used),
      put(?NT_USED, sets:add_element(Fresh, Used)),
      erl_syntax:variable(Fresh).
  
  new_underscore_variable() ->
      Used = get(?NT_USED),
      new_underscore_variable(Used).
  
  new_underscore_variable(Used) ->
  