Don't use this module. It has an overloaded API, which uses global variables. Look at Net::IDN::Punycode and Net::IDN::Encode instead.
(NB: I'm the current maintainer.)
Don't use these modules. Seriously.
All of these modules use X11 colour names for input, which are not fully compatible with SVG/CSS colour names. This is often surprising, especially for the ::html module.