Say you implement this. Then you want to copy files which have ACLs (Access Control Lists) attached. Now you have to fix File::Copy again to copy the ACLs too. Tomorrow, what other file metadata will be employed at the filesystem level?
IMHO, it doesn't make sense to worry about tomorrow problems if you don't know what they will be (well, at least with a fair amount of probability). <AFAIK>ACLsare still different from OS to OS, and somewhere they can be considered experimental;</AFAIK> it is a moving target, that one can plan to address only where it is stable enough.
By the way, UNIX file permissions are there from the start, on every flavour of UNIX, and that problem on File::Copy should be addressed...
The very nature of Perl to be like natural language--inconsistant and full of dwim and special cases--makes it impossible to know it all without simply memorizing the documentation (which is not complete or totally correct anyway).
--John M. Dlugosz