Try Spreadsheet::SimpleExcel
I found it has both add_row (per documentation)

# append data to 'NAME'
  $excel->add_row('NAME',[qw/new row/]);
[download]

and add_row_at (per documentation)

# add a row into the middle
  $excel->add_row_at('Name of Worksheet',1,[qw/new row/]);
[download]