I neglected to respond to this point in my other post:

however, it would seem that if you can live without 'use locale;' that would be a good thing.

I'm in full agreement here, and don't use it my own code. It's the side effect it being called in another package (Gtk2 in this case) that triggered the issue with my own system.

salva's recommendation of using no locale in 11119943 and 11119948 looks good to me, and I'll be reaching for it next time I strike this issue.