--- each_key { |subkey, wtime| ... }
    Υ֥󤷤ޤ
    
    subkey ϥ֥̾ɽ String Ǥ
    wtime Ϻǽɽ FILETIME (64-bit ) Ǥ
    (Registry.wtime2time [Win32::Registry/Registry.wtime2time])

