Can't call method "isa" on an undefined value at /usr/local/share/perl/5.8.8/Class/Std.pm line 225.

##</code><code>##

# This is the values that blow it up
#   @hierarchy = qw(EEBL::League::Schedule);
#   @hierarchy = qw(EEBL::Team EEBL EEBL::Config);

    return @{$_hierarchy_of{$class}}
        = sort { $a->isa($b) ? -1
               : $b->isa($a) ? +1
               :                0
               } @hierarchy;