Suppose the XML file is:

```
<class name=math>
<student>luke1</student>
...
<student>luke8000000</student>
</class>
<class name=english>
<student>mary1</student>
...
<student>mary1000000</student>
</class>

```

after `class=math` is parsed, I want to delete this element from the XML file so that when `class=english` is parsed, Twig will not go through the content of `class=math`.

The reason I want to do this is that, so far even if I use `TwigRoots => {"class[\@name='english']" => \&counter}` I still need to wait a long time for Twig to start to parse `class=english` because it needs to go over each line of `class=math` (correct me if it does not need to go over each line). In the actual file I run, there are several classes, I do not want to let Twig go through each line in `class=math` before finding the class it is really interested in.

Thanks in advance.