private static UnifiedExpression CreateDregxOnce(XElement node)
        {
            Contract.Requires(node != null);
            Contract.Requires(node.Name() == "dregx_once");
            // TODO: Implement correctly
            var str = node.Value;

            return(UnifiedRegularExpressionLiteral.Create(str));
        }
        private static UnifiedExpression CreateRegexp(XElement node)
        {
            Contract.Requires(node != null);
            Contract.Requires(node.Name() == "Regexp");
            // TODO: Implement correctly
            var str = node.Value;

            return(UnifiedRegularExpressionLiteral.Create(
                       str.Substring(7, str.Length - 8)));
        }