Oh, I see... warnings were turned off in XML::Twig or some other module that I'm calling and the global '-w' is turning them back on... Somehow I was expecting all major modules to have warnings turned on already, so I kept thinking of '-w' as redundant, and never tried it.

Now that I can reproduce it by hand I've tracked down at least one of the spew causes to XML::Twig::first_elt, so I'll go file a bug on that. Thanks.