The documentation for IIS seems to indicate that for some time there have been some headaches with IIS and that some manual configuration can be needed.
They made this tool to help with that:
http://docs.activestate.com/activeperl/5.10/bin/ap-iis-config.html
Have you tried using this? Perhaps it can help you.
Here is a relevant blog post about it:
http://www.activestate.com/blog/2010/06/setting-iis-activeperl