You will have to give us the error message, XML::Parser does not care about the size of the overall file, just about the size of the current stack of open elements. So the only way you can get it to use lots of memory is by having a very, very, VERY, deep document.

You can do a top while the document is being parsed and see if that's the problem, but I doubt it very much.

Big documents tend to come with a higher risk of real XML error than small ones ;--(