thread.rb

@start = false

t1 = Thread.new do
  while !@start
    sleep 0.001
  end

  puts 'started 1'
end

t2 = Thread.new do
  while !@start
    sleep 0.0001
  end

  puts 'started 2'
end

puts 'Ready'; sleep 0.3
puts 'Set'; sleep 0.3
puts 'Go'; sleep 0.3

@start = true

t1.join
t2.join