--- The application currently has three modes. The default, Regex, will
--- compute a regular expression matching the input CIDRs. Reduce, on
--- the other hand, will combine any redundant/adjacent CIDR blocks
--- into one. Dupe will show you what would be removed by Reduce.
-data Mode = Regex | Reduce | Dupe
+-- | The application currently has four modes. The default, Regex,
+-- will compute a regular expression matching the input
+-- CIDRs. Reduce, on the other hand, will combine any
+-- redundant/adjacent CIDR blocks into one. Dupe will show you what
+-- would be removed by Reduce, and Diff will show both additions and
+-- deletions in a diff-like format.
+data Mode = Regex | Reduce | Dupe | Diff