It seems that you went wrong somewhere in the directions, as Perl does not find the module.

Also, you have not told us whether all target machines will be Mac computers (running the same version of OSX, on the same processor type, Intel or PowerPC). If you create an application using these OSX-specific modules, your application will not run anywhere else.

More cross-platform user interfaces can be created by using HTTP+CGI, but this means you will have to run a webserver in addition to the main program. Also you can look into Tk, but that means that your application will not look native unless you give extra care. People had good success using Wx, but I'm not sure how well it works on OSX.