From the docs for XML::Simple–

What isn't XML::Simple good for?

The main limitation of XML::Simple is that it does not work with 'mixed content' (see the next question). If you consider your XML files contain marked up text rather than structured data, you should probably use another module.

If you are working with very large XML files, XML::Simple's approach of representing the whole file in memory as a 'tree' data structure may not be suitable.

XML::Twig and XML::LibXML are both better options for most XML processing, not just large files.