Marshall's helpful debugging should have gotten you closer, at least. :-) That said, do note that XML::LibXML has lots of backward compatibility interfaces and it's fairly complex to work with. There's one small change that can help your case:

In your buildXMLElements sub call, you're passing in the parent element directly as it is and appending child elements into it. If you pass in a ref to it instead, you can see your <CHARGE> elements appear.

HTH. Good luck and have fun!