One misinterpretation was that Flyweight objects are necessarily small. Nope. It suffices that they contain only intrinsic, immutable state, and that the client pass in extrinsic state to perform whatever operations need it. Pattern title aside, there's nothing in the pattern that dictates size.
The XSLT Cookbook is bedside, and continues to boggle and amuse. People complain that Perl is complicated? Sheesh.