src/main/java/com/bazaarvoice/jless/parser/Parser.java
Rule URL() {
        return Sequence(
                Sequence(
                        "url(", Ws0(),
                        FirstOf(
                                String(),
                                OneOrMore(FirstOf(AnyOf("-_%$/.&=:;#+?"), Alphanumeric()))
                        ), Ws0(),
                        ')'
                ),
                push(new SimpleNode(match()))
        );
    }
Rule URL() {
        return Sequence(
                Sequence(
                        "url(", Ws0(),
                        FirstOf(
                                String(),
                                OneOrMore(FirstOf(AnyOf("-_%$/.&=:;#+?"), Alphanumeric()))
                        ), Ws0(),
                        ')'
                ),
                push(new SimpleNode(match()))
        );
    }
Rule URL ( ) { return Sequence ( Sequence ( "url(" , Ws0 ( ) , FirstOf ( String ( ) , OneOrMore ( FirstOf ( AnyOf ( "-_%$/.&=:;#+?" ) , Alphanumeric ( ) ) ) ) , Ws0 ( ) , ' ' ) , push ( new SimpleNode ( match ( ) ) ) ) ; }
'url(' (String / [-_%$/.&=:;#+?Alphanumeric]+) ')'
url ( ( String / [ - _%$ / . & = : ; # + ?Alphanumeric ] + ) )