+-- | Some exit codes, used in the ExitFailure constructor.
+module ExitCodes
+where
+
+-- | One of the CIDRs is invalid (malformed, not a CIDR at all, etc).
+exit_invalid_cidr :: Int
+exit_invalid_cidr = 1
+
+-- | We were unable to parse the command-line arguments.
+exit_args_parse_failed :: Int
+exit_args_parse_failed = 2