anchor.diff:    ;
   
   event_control
  -  : AT_SIGN hierarchical_event_identifier
  +  : AT_SIGN hierarchical_identifier
     | AT_SIGN LPAREN event_expression RPAREN
     | AT_SIGN MUL
     | AT_SIGN LPAREN MUL RPAREN
  
positive.code: 
  ps_or_hierarchical_net_identifier
    : package_scope? net_identifier
    | hierarchical_net_identifier
    ;
  
  ps_or_hierarchical_property_identifier
    : package_scope? property_identifier
    | hierarchical_property_identifier
    ;
  
  ps_parameter_identifier
  
negative.code:   ;
  
  variable_concatenation_value
    : hierarchical_identifier
    | hierarchical_identifier LSQUARE expression RSQUARE ( LSQUARE expression RSQUARE )*
    | hierarchical_identifier LSQUARE expression RSQUARE ( LSQUARE expression RSQUARE )* LSQUARE range_expression RSQUARE
    | hierarchical_identifier LSQUARE range_expression RSQUARE
    | variable_concatenation
    ;
  
  