use strict;
use warnings;

use Win32::OLE;
use Win32::OLE::Variant;

use constant CLSID_ACTIVEDESKTOP   => '{75048700-EF1F-11D0-9888-006097DEACF9}';
my $actdesktop = Win32::OLE->new(CLSID_ACTIVEDESKTOP) or die();
$actdesktop->SetWallpaper('C:\WINNT\winnt256.bmp');