Quoth perldoc perldoc:

 -U run insecurely
   Because perldoc does not run properly tainted, and is known to
   have security issues, it will not normally execute as the supe-
   ruser.  If you use the -U flag, it will do so, but only after set- 
+       
   ting the effective and real IDs to nobody's or nouser's account,
   or -2 if unavailable.  If it cannot relinquish its privileges, it
   will not run.
[download]