src/main/java/com/bazaarvoice/jless/parser/Parser.java
Rule Parameters() {
        return Sequence(
                '(',
                Parameter(), push(new ParametersNode(pop())), Ws0(),
                ZeroOrMore(
                        ',', Ws0(),
                        Parameter(), peek(1).addChild(pop())
                ),
                ')',
                push(new ScopeNode(pop()))
        );
    }
Rule Parameters() {
        return Sequence(
                '(',
                Parameter(), push(new ParametersNode(pop())), Ws0(),
                ZeroOrMore(
                        ',', Ws0(),
                        Parameter(), peek(1).addChild(pop())
                ),
                ')',
                push(new ScopeNode(pop()))
        );
    }
'(' Parameter Ws0 (',' Ws0 Parameter)* ')'