code: Rule variableDefinition() {
  		return Sequence(
  				group.types.type().label("type"),
  				variableDefinitionPart().label("head"),
  				ZeroOrMore(Sequence(
  						Ch(','), group.basics.optWS(),
  						variableDefinitionPart()).label("tail")),
  				set(actions.createVariableDefinition(value("type"), value("head"), values("ZeroOrMore/tail"))));
  	}
docs: Add your own modifiers!