foo.rb

Thread.abort_on_exception = true

begin
  t1 = Thread.new do
    t2 = Thread.new do
      sleep 5
      puts "RAISE"
      1/0
    end
    sleep 3
    puts "WAITING T2"
    t2.join
  end

  sleep 1
  puts "WAITING T1"
  t1.join
rescue => e
  puts "ERROR "+e.message
end

puts "FINISHED"

########################
# TWO POSSIBLE OUTPUTS
########################
#
# Case A
#
# WAITING T1
# WAITING T2
# RAISE
# ERROR divided by 0test.rb:8:in `/': divided by 0 (ZeroDivisionError)
#   from test.rb:8:in `block (2 levels) in <main>'
#
########################
#
# Case B
#
# WAITING T1
# WAITING T2
# RAISE
# ERROR divided by 0
# FINISHED
#
########################