i can't find anything about libraries in there. don't misunderstand me, it's a good tutorial, but the OP seems to have previously installed XML::Simple successfully, so i guess they're familiar with module installing, so in this case your answer wouldn't really help the OP.
i think the question was, like Cody Pendant said, about installing libraries that are needed by XML::Smart. of course this is not so much related to perl but rather an OS related question, but i also had problems installing XML::Smart, and it would be nice to have a tutorial or a collection of helpful links on that topic.