perldoc perlrun says:

-U

allows Perl to do unsafe operations. Currently the only "unsafe" operations are the unlinking of directories while running as superuser, and running setuid programs with fatal taint checks turned into warnings.

So I think you should file a bug report against Perl saying that linking directories as superuser should also be "unsafe".

Oh, and next time you won't have to resort to C to undo the problem. (:

                - tye