use Encode;
use Win32::OLE;
$ex = Win32::OLE->new('Excel.Application');
$book = $ex->Workbooks->Add;   
$sheet = $book->Worksheets(1);
$text="árvíztűrő tükörfúrógép";
@encodings= Encode->encodings(":all");
$line=1;

foreach (@encodings) {
    $sheet->Cells($line++,1)->{Value}=$_;
    $sheet->Cells($line-1,2)->{Value}=encode($_,$text);
};
$book->SaveAs('c:\test.xls');