...
my $sheet = [];
foreach my $row_index ($source_sheet->row_range) {
  my $row = [];
  foreach my $col_index ($source_sheet->col_range) {
   my $source_cell = $source_sheet->{Cells}[$row_index][$col_index];
   if ($source_cell)
   {
    #print "( $row_index , $col_index ) =>", $source_cell->Value, ",";
    push @$row, $source_cell->Value;
   }
  } 
  push @$sheet, $row;
}

csv( in => $sheet, out => 'file.csv' );