Since it appears you are stuck with XML::Simple, you may also wish to look at:

XML::Simple is doing too much for me! Help please.
XML::Simple "transforming data"
XML::Simple help

for more on XML::Simple and its Keeproot, ForceArray, RootName, and NoAttr options.

These might also be helpful:

Perl-XML Frequently Asked Questions
Frequently Asked Questions about XML::Simple

HTH,