http://search.cpan.org/~reneeb/Spreadsheet-SimpleExcel-1.9/lib/Spreadsheet/SimpleExcel.pm#set_headers
$excel->sort_data('Name of Worksheet',1,'ASC');
$excel->sort_data('Name of Worksheet',1,'ASC');
$excel->sort_data('Name of Worksheet','DESC');
sort_data
# sort data of worksheet - ASC or DESC
$excel->sort_data('Name of Worksheet','DESC');
sort_data sorts the rows. All sorts for one worksheet are combined,so
$excel->sort_data('Name of Worksheet','DESC');
$excel->sort_data('Name of Worksheet','ASC');
will sort the column 0 first and then (within this sorted data) the column 1.