Update: I misread the question, sorry for the noise; please ignore

Note: "unlink" will not attempt to delete directories unless you are superuser and the -U flag is supplied to Perl. Even if these conditions are met, be warned that unlinking a directory can inflict damage on your filesystem. Finally, using "unlink" on directories is not supported on many operating systems. Use "rmdir" instead.

Do you have any suggestions on how that could have been formulated more clearly, or at a more appropriate place in the documentation?