use Win32::OLE qw(in with);
use Win32::OLE::Const 'Microsoft Excel';
$Constant = Win32::OLE::Const->Load('Microsoft Excel');
$Excel = Win32::OLE->new('Excel.Application', 'Quit') ||
die "Error launching MS Excel ".Win32::OLE->LastError; 

$hwnd = $Excel->{"Hwnd"};
print "Excel Windows Handle: $hwnd\n";