#!perl
use strict;
use Excel::Writer::XLSX;
my $workbook = Excel::Writer::XLSX->new( 'sample.xlsx' );
$workbook->add_worksheet("new");
$workbook->add_worksheet("old");

# select the sheet
my $worksheet = $workbook->sheets(0);
$worksheet->write(2, 2, 'This is Sheet 1');

# or directly
$workbook->sheets(1)->write(2, 2, 'This is Sheet 2');;