use Win32::OLE;

my $book;
my $sheet;
my $sheet_name = "rota";
my $rota_location = 'e:/rota.xls';

if( -e $rota_location ){
    $book = $ex->Workbooks->open($rota_location);    
}else{
    $book = $ex->Workbooks->Add;
}

unless($sheet = eval { $book->Worksheets($sheet_name) }){
    $sheet = $book->Worksheets->Add;
    $sheet->{Name} = $sheet_name;
}