src/main/java/com/bazaarvoice/jless/parser/Parser.java
Rule ExpressionFunction() {
        return Sequence(
                Sequence(
                        "expression(",
                        ZeroOrMore(
                                TestNot(
                                        ')',
                                        Ws0(),
                                        AnyOf(";}")
                                ),
                                ANY
                        ),
                        ')'
                ),
                push(new SimpleNode(match()))
        );
    }
Rule ExpressionFunction() {
        return Sequence(
                Sequence(
                        "expression(",
                        ZeroOrMore(
                                TestNot(
                                        ')',
                                        Ws0(),
                                        AnyOf(";}")
                                ),
                                ANY
                        ),
                        ')'
                ),
                push(new SimpleNode(match()))
        );
    }
'expression(' (!(')' Ws0 [;}]) .)* ');'