Thread.abort_on_exception= in Ruby 1.9

Hi,

Thread.abort_on_exception=true is not working the way I would expect it 
to in Ruby 1.9 (my build is from 7/24).

Is this "just a bug" or a "not yet implemented" issue or is it a more 
fundamental problem exposed by YARV's use of native threads?  That is, 
should we treate abort_on_exception= as a non-portable method useful 
only for implementations that use green threads?

Here's the test code I'm using:

Thread.abort_on_exception = true

t = Thread.new {
   sleep 1
   raise "boom"
}

t.abort_on_exception = true

sleep 2
puts "done"

It goes "boom" in Ruby 1.8:

$ ruby -v boom.rb
ruby 1.8.6 (2007-03-13 patchlevel 0) [i686-linux]
boom.rb:5: boom (RuntimeError)
         from boom.rb:3:in `initialize'
         from boom.rb:3:in `new'
         from boom.rb:3

But it prints "done" in Ruby 1.9:

$ ruby1.9 -v boom.rb
ruby 1.9.0 (2007-07-24 patchlevel 0) [i686-linux]
done