-# read list of newsgroups from --checkgroups
-# into a hash reference
-my $ValidGroups = &ReadGroupList($OptCheckgroupsFile) if $OptCheckgroupsFile;
+# honor $OptCheckgroupsFile,
+# warn for $OptSums if set concurrently
+my $ValidGroups;
+if ($OptCheckgroupsFile) {
+ # read list of newsgroups from --checkgroups
+ # into a hash reference
+ $ValidGroups = &ReadGroupList($OptCheckgroupsFile);
+ &Bleat(1,"--sums option can't possibly work with --checkgroups option set")
+ if $OptSums;
+}