A good point you have here.

As long as all the DLL's are in the perl-tree and are "dynaloaded" it will work, but I can imagine that some modules might put the DLL's elsewhere and then simply copying the perl-tree will not work.

I was thinking of things like expat or sablotron which use their own dll's in their own folders and with which I had no end of trouble getting them to run after I upgraded my perl-installation.