+PH/22 Guard against possible overflow in moan_check_errorcopy().
+
+PH/23 POSIX allows open() to be a macro; guard against that.
+
+PH/24 If the recipient of an error message contained an @ in the local part
+ (suitably quoted, of course), incorrect values were put in $domain and
+ $local_part during the evaluation of errors_copy.
+