gistfile1.js

            var CLASS_NAME = "className",
                BOUNDING_BOX = "boundingBox",
                SKIN_PREFIX = "yui-skin-",
                // ideally get [\s^] to work, instead of non-capturing group
                SKIN_REGEXP = new RegExp("(?:^|\\s)(" + SKIN_PREFIX + "[^\\s$]+)");

            ...

            getSkinClass : function() {
                var match;
                this.get(BOUNDING_BOX).ancestor(
                    function(n) {
                        match = n.get(CLASS_NAME).match(SKIN_REGEXP);
                        return match;
                    }
                );
                return (match && match[1] || null);
            }