String prefix = asString(getArg(arguments, 1));
        CompiledScript script = Compiler.compile(expression);
        try {
            Stack stack = new ListStack();
            if (prefix != null)
                context = new RelativeExpressionContext(context, prefix);
            script.run(stack, context);
            return stack.pop();
        } catch (ExecutionException ee) {
            return null;
        }
    }