Why Is Ruby Multithreading Slow?

And I decided to run it with ruby 't.rb' instead of from within irb. Of course, I didn’t get what I expected — I got no output at all, and my program exited immediately. It didn’t take me long to figure out the problem — the main thread exiting before the other threads ever got the processor — or to fix it by adding [producer, printer1, printer2].each { |t| t.join } to the end of the script.