code: Rule Userdef() {
  		return Sequence(UserdefSymbol(),
  				ZeroOrMoreS(WSP()).suppressNode(),
  				String("="),
  				ZeroOrMoreS(WSP()).suppressNode(),
  				FirstOfS(
  					//SequenceS(String("!"), LongGracing(), String("!")),
  					Gracing(),
  					ChordOrText())
  		).label(Userdef);
  	}
docs: userdef ::= userdef-symbol *WSP "=" *WSP (long-gracing / chord-or-text)