anchor.diff:                  TOKMODULE typevar_item_or_var
                   [ formal_list ]
                   [ provisos_clause ] SEMICOLON
  -                (   method_declaration
  -                |   interface_declaration [SEMICOLON]
  -                |   TOKPARAMETER VAR  equal_value SEMICOLON
  -                |   TOKDEFAULT_CLOCK [ VAR ] [ var_list ] [ equal_value ] SEMICOLON
  -                |   TOKINPUT_CLOCK [VAR] var_list equal_value SEMICOLON
  -                |   TOKOUTPUT_CLOCK VAR var_list SEMICOLON
  -                |   TOKNO_RESET SEMICOLON
  -                |   TOKSCHEDULE import_arg
  -                      ( TOKCF | TOKSB | TOKSBR | TOKC ) import_arg SEMICOLON
  -                |   TOKDEFAULT_RESET VAR var_list  [ equal_value ] SEMICOLON
  -                |   TOKINPUT_RESET [ VAR ] var_list [ TOKCLOCKED_BY var_list ]
  -                      equal_value SEMICOLON
  -                |   TOKOUTPUT_RESET VAR var_list TOKCLOCKED_BY var_list SEMICOLON
  +                ( method_declaration
  +                | interface_declaration [SEMICOLON]
  +                | TOKPARAMETER VAR  equal_value SEMICOLON
  +                | TOKDEFAULT_CLOCK [ VAR ] [ var_list ] [ equal_value ] SEMICOLON
  +                | TOKINPUT_CLOCK [VAR] var_list equal_value SEMICOLON
  +                | TOKOUTPUT_CLOCK VAR var_list SEMICOLON
  +                | TOKNO_RESET SEMICOLON
  +                | TOKSCHEDULE import_arg ( TOKCF | TOKSB | TOKSBR | TOKC ) import_arg SEMICOLON
  +                | TOKDEFAULT_RESET VAR var_list  [ equal_value ] SEMICOLON
  +                | TOKINPUT_RESET [ VAR ] var_list [ TOKCLOCKED_BY var_list ] equal_value SEMICOLON
  +                | TOKOUTPUT_RESET VAR var_list TOKCLOCKED_BY var_list SEMICOLON
                   )*
                   TOKENDMODULE [ COLON  VAR ]
               )
  
positive.code:             statement_list
              TOKENDACTION [ COLON VAR]
          | TOKACTIONVALUESTATEMENT statement_list TOKENDACTIONVALUE
  
      rule single_statement:
            case_statement
          | TOKFOR LPAREN
                  for_decl_item (COMMA for_decl_item)* SEMICOLON
                  assign_rvalue SEMICOLON
                  for_variable_assignment ( COMMA for_variable_assignment )*
  
negative.code:         [ formal_list ]
          [ provisos_clause ]
          ( equal_value SEMICOLON
          | SEMICOLON [ ( single_statement)+ TOKENDFUNCTION [ COLON  function_name] ]
          )
  
      rule import_arg:
  