anchor.diff:             {{t,11},2},
              {{t,12},4},
              {{t,13},1}] =
  -        analyse_expr(<<"<< \n" % 1 (now: 0)
  +        analyse_expr(<<"<< \n" % 1
                          " << (2)\n" % 4 (now: 0)
                          "     :(8) >> || \n"
                          "    <<X>> <= << 1,\n" % 1
  
positive.code: 
      %% The template cannot have a counter since it is not allowed to
      %% be a block.
      ?line [% {{t,1},1},
             %% {{t,2},2},
             {{t,3},1},
             {{t,4},1},
  
negative.code:                        "    true >>.\n" % 2
                         "two() -> 2">>, Cf),
  
      ?line [{{t,1},1},
             %% {{t,2},4},
             {{t,4},1},
             {{t,6},1},
  