As mirod and Elian have observed, limited memory leading to swapping is the most likely cause of the problem. If you slurp the whole document into a document tree then you'll likely have exactly the same problems regardless of which module you use for parsing. However, the main point of XML::Twig is to enable you to reap the benefits of a tree based model without having to have the whole file in memory. With judicious use of the twig_roots mode, you can have XML::Twig hand your code a tree representation of one section of the document. When you've finished working with that section, discard it and the memory will be reused for the next section.