rb.rb

r = Ractor.new do
  # Two pipes a piping...
  pipes = Array.new 2 do
    Ractor.new do
      loop do
        Ractor.yield Ractor.receive
      end
    end
  end

  loop do
    # Pick a pipe at random to send to...
    pipes.sample << Ractor.receive
    # And select a pipe to receive from...
    _pipe, response = Ractor.select(*pipes)
    Ractor.yield response
  end
end

r.send :test

100_000.times { r.send r.take }

r.take
#=> :test