There should not be more than 1 root element in a proper XML file. If that is what you mean by "many trees", otherwise mirod has a few posts here on pm regarding how to process XML in chunks. When I started with XML::Twig, I read all his posts here and that answered every question. If you have perldoc, you can look at the twig page and search for flush and purge. I can't seem to reach xmltwig.com for the last week from around here, so I can't link those examples.