thr = Thread.new{}
# thread dies

"HERE" if not thr or not thr.alive? # this works!!
"HERE" unless thr or thr.alive? # doesn't work!! WHY?
"HERE" unless thr and thr.alive? # works, but why?

I dont see why the unless/and works when the unless/or should be the one 
short-circuting no?

Thanks,

Zach