diff -bu Tangram-2.10-fjDp7t/lib/Tangram/Schema.pm~ Tangram-2.10-fjDp7t/lib/Tangram/Schema.pm
--- Tangram-2.10-fjDp7t/lib/Tangram/Schema.pm~	2006-03-28 23:05:29.000000000 -0600
+++ Tangram-2.10-fjDp7t/lib/Tangram/Schema.pm	2013-07-23 14:54:41.530323494 -0500
@@ -185,7 +185,7 @@
 sub classdef
 {
    my ($self, $class) = @_;
-   return $self->{classes}{$class} or confess "unknown class '$class'";
+   return $self->{classes}{$class} || confess "unknown class '$class'";
 }
 
 *get_class_by_name = \&classdef;