#move this line up (and simplify it):
   #if(length($materialmapping_file) gt 0 or length($data_folder) gt 0)
   unless (defined $materialmapping_file and defined $data_folder)
   {
      print "Usage: $0 <materialmapping_file> <data_folder>\n";
      exit;
   }

   # Now, everything that follows can be outdented one level.