I wonder if with perl is possible to detect user screen resolution?

While this isn't possible in general, earlier today I happened across an exception while playing with a friend's Danger Hiptop. The Hiptop, through the Danger proxy server, sends Http-X-AvantGo-Screensize. The contents are the Base64-encoded screen dimension.

  use MIME::Base64;
  print decode_base64($ENV{'HTTP_X_AVANTGO_SCREENSIZE'});
[download]

prints

  240x320
  P
[download]

I have no idea what the 'P' is. A google search turned up no useful info.