load external sub. when you install package without scanner optimized into main
binary, you will lose performance but still have system up.

--- qmail-scanner-2.03/qmail-scanner-queue.template~	2008-05-06 07:39:32.000000000 +0300
+++ qmail-scanner-2.03/qmail-scanner-queue.template	2008-05-06 07:41:12.329295604 +0300
@@ -1148,6 +1148,15 @@
   }
   &debug("ini_sc: recursively scan the directory $ENV{'TMPDIR'}/");
 
+  for (@scanner_array) {
+    unless (defined &$_) {
+      my $s = $_;
+      $s =~ s/_scanner$//;
+      &debug("ini_sc: load $s sub");
+      require "/usr/lib/qmail-scanner/sub-$s.pl";
+    }
+  }
+
   #Run AV scanners - even if the message is already going to be quarantined
   #due to some Policy: this way you get the definitive answer as to what is
   #a virus... The exception to this is if it looks like a DoS attack - then