-.IP \(bu 2
-\fBReversed\fR
-.P
-Perform reverse DNS (PTR) lookups on the IP addresses contained within
-the given CIDRs.
-.P
-.nf
-.I $ hath reversed <<< \(dq198.41.0.4/30\(dq
-198.41.0.4: a.root-servers.net.
-198.41.0.5:
-198.41.0.6: rs.internic.net.
-198.41.0.7:
-.fi
-.P
-The DNS lookups are usually the bottleneck for this mode, but we can
-perform them in parallel. Simply pass the number of threads to the GHC
-runtime on the command line; for example, the following will perform
-25 lookups in parallel: