LINE 1 won't be extracted (before first ON code)
..exon..
LINE 2 will be extracted (within ON/OFF codes)
LINE 3 will be extracted (within ON/OFF codes)
..exoff..
LINE 4 won't be extracted (not within ON/OFF codes)
..exon..
LINE 5 will be extracted (within ON/OFF codes)
LINE 6 will be extracted (last of 4 such lines)
..exoff..
..exdone..
LINE 7 won't be extracted (after DONE code)
..exon..
LINE 8 won't be extracted even though within ON/OFF codes (after DONE code)
..exoff..