--- Process.detach(pid)

    ruby 1.8 feature

    ҥץ pid νλƻ뤹륹åɤ֤ޤ
    åɤϻҥץλ nil ǽλޤ
    (ꤷҥץ¸ߤʤ¨¤ nil ǽλޤ)

        pid = fork {
          # child
          sleep 3
        }

        th = Process.detach(pid)
        p th.value

        # => nil

