Print crap before readline

readline-prefixed-junk.rb

#!/usr/bin/env ruby

require 'readline'

run = true
puts
worker = Thread.new do
  i = 0
  while run
    STDOUT.print("\e[s\r\e[A\e[KMoo moo baa #{i += 1}\n\e[u");
    sleep 1
  end
end

out = Readline.readline("Moo: ")
run = false
worker.join
puts "Read: #{out.inspect}"