use Modern::Perl '2014';
use Spreadsheet::ParseExcel::Simple;
use Spreadsheet::WriteExcel;

my $xls_in  = Spreadsheet::ParseExcel::Simple->read('./spreadsheet_in.xls');
my $xls_out = Spreadsheet::WriteExcel->new('./spreadsheet_out.xls');

foreach my $sheet ( $xls_in->sheets ) {
    my $active_sheet = $xls_out->add_worksheet();
    my @sheet_data;
    while ( $sheet->has_data ) {
        my @data = $sheet->next_row;
        push @sheet_data, \@data;
    }
    push @sheet_data, ['This data is added at the end'];
    $active_sheet->write_col( 0, 0, \@sheet_data );
}

$xls_out->close();