# File lib/em-hiredis/pubsub_client.rb, line 86
    def psubscribe(pattern, proc = nil, &block)
      if cb = proc || block
        @psub_callbacks[pattern] << cb
      end
      @psubs << pattern
      raw_send_command(:psubscribe, [pattern])
      return pubsub_deferrable(pattern)
    end