Example in documentation has error

[martinstreicher]

This code, found in the description of concurrency techniques, does not work as-is:

require 'fiber'

ping = Fiber.new { loop { puts "ping"; pong.transfer } }
pong = Fiber.new { loop { puts "pong"; ping.transfer } }
ping.transfer

pong is undefined.

This works:

ping = pong = nil  # or just `pong = nil`
ping = Fiber.new { loop { puts "ping"; pong.transfer } }
pong = Fiber.new { loop { puts "pong"; ping.transfer } }
ping.transfer