This seems to me to be an ideal application of XPath expressions, especially since you say that “E-H have a different XML template to follow.” (If there are two variations to deal with now, one day there will be three and then four.) With this approach, the expressions define what you are looking for, and it becomes XPath’s job to find it. This will probably very-considerably simplify your logic overall, because the structure of your program is no longer matched to that of the file, and does not change as the files inevitably do. All you need is an expression, perhaps in a list of them, that will succeed for a particular file. (XML::LibXML is my recommendation but not the only choice.) Notice also that the structure of the expression does not have to consider the entire structure of the surrounding file, either: “tell me what you’re looking for, and I can find it, wherever it is.”
Another thread, today, mentioned XML::XSH, which seems to include a shell for applying XPath expressions interactively, among other features. I haven’t (yet!) looked into that, but I want to include a link to it here anyhow.