I am kind of wrapping stat() for a filesystem overlay, FUSE, Filesys::Virtual, client and server script stuff.

You are right: The easy way would be to just use -d and -f, as you pointed out, and equal them to my own breed of flags - right. (already tried that and it worked)

But I would like to stay away from introducing my own lingo and instead stick to standards. As of now, I only need the differentiation between file/dir, but in the future I might needed to have more resolution in that field. And starting my own flags now would lead to reinventing the whole "mode" thing in the future...