Thanks for the good question, Courage; I should have mentioned that. I can't really give an authoritative answer about the internals of App::Packer, but I'll tell you what I know :-)
App::Packer does use compression. My guess is that the main perl file and the module sources are all inside the executable file, in a compressed form. Smaller apps (I quickly tried one that uses a very small test module) don't seem to create temporary files. However, another app I "packaged" that uses Wx, XML::Parser and File::Spec) creates three temporary DLL files upon startup.
Hope that helps...
By the way -- thanks to the perl monks for the warm reception of this tutorial. I asked myself whether I should write it or not, and then decided to just do it, even if it is just to get it sorted out for myself again. The response encouraged me to be not so hesitant in the future.