Prima is an extensible Perl toolkit for multi-platform GUI development.
Platforms supported include Linux, Windows NT/9x/2K, OS/2 and UNIX/X11
workstations ( FreeBSD, IRIX, SunOS, Solaris  and others). The toolkit 
contains a rich set of standard  widgets and has  emphasis on 2D image
processing tasks.  A Perl program using PRIMA looks and behaves identically 
on X, Win32 and OS/2 PM.  The toolkit includes a visual builder ( VB ) and 
a graphic pod viewer utility ( podview ). The examples are installed into 
perl site in Prima/examples directory. 
A 'hello world' code is as simple as follows:

   use Prima qw(Application Buttons);
   Prima::Window-> create(
      text     => 'Hello world!',
      size     => [ 200, 200],
   )-> insert( Button =>
      centered => 1,
      text     => 'Hello world!',
      onClick  => sub { $::application-> close },
   );
   run Prima;

WWW: http://search.cpan.org/dist/Prima/
WWW: http://prima.eu.org/