# open file in read/write mode
open(my $xlshandle, '+<', $xlsfile) or die "Can't open '$xlsfile' for read/write: $!\n";
binmode($xlshandle);
# insert code to read spreadsheet
# reset handle to beginning of file
seek($xlshandle, 0, 0);
my $newxls = Spreadsheet::WriteExcelXML->new($xlshandle); # handle, NOT file
# insert code to put updated data into $newxls
$newxls->close();
close($xlshandle);

##</code><code>##

my $newxlsfile = $xlsfile . '.new';
my $newxls = Spreadsheet::WriteExcelXML->new($newxlsfile); # file, NOT handle
# insert code to put updated data into $newxls
$newxls->close();
close($xlshandle);
rename($xlsfile, $xlsfile . '.bak');
rename($newxlsfile, $xlsfile);