You can use OLE as mentioned. Also you can consider using Spreadsheet::ParseExcel to read the spreadsheet in and and Spreadsheet::WriteExcel to write an amended spreadsheet out.

E.g. code like this

my $file = "infile.xls";
my $excel = Spreadsheet::ParseExcel::Workbook->Parse($file)
  || die "cannot parse $file: $!";
my $sheet = $excel->{Worksheet}->[0];
my $sheetname = $sheet->{Name};
my $val1 = $sheet->{Cells}[0][2]->{Val};

my $workbook = Spreadsheet::WriteExcel->new("outfile.xls");
my $worksheet = $workbook->add_worksheet();
my $rowno = 1;
my $colno = 0;
$worksheet->write($rowno, $colno, 'some value');
my $dateformat = $workbook->add_format();
$dateformat->set_num_format('0000');
$worksheet->write(2,0,'02');
$workbook->close;
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Regards, Peter