Hmm.. no idea. :-) I don't actually have the module installed myself, just wrote the above source from the Mail::Bulkmail POD and the bits you provided. I'm not sure why this happens, although I figure it's because rather than a filename it's passing an array reference as the address list. According to the documentation, that is allowed (as would have been passing a coderef). If I had the module, I'd look into it.. maybe tonight when I'm home again.

Update: Duh, of course.

Makeshifts last the longest.