Use the tighter-binding or

diff --git a/web/usage.cgi b/web/usage.cgi
index 2123506..af8901b 100755 (executable)
--- a/web/usage.cgi
+++ b/web/usage.cgi
@@ -82,7 +82,7 @@ if ($type{"sub_types"}) {
 }
 
 foreach my $sub_type (@sub_types) {
-  my $cdef = $sub_type->{"cdef"} or $type{"cdef"};
+  my $cdef = $sub_type->{"cdef"} || $type{"cdef"};
   my $suffix = $sub_type->{"suffix"};
 
   my $path = catfile(GRAPH_DIR, "*-$type{plugin_name}-uuid_$uuid$suffix-?.rrd");