$ for i in 8 10 12 14 16 18 20; do perl scripts.pl scripts-5$i.txt >5$i.lst; done
$ for i in 8 10 12 14 16 18; do diff --unchanged-line-format= --new-line-format=%L 5$i.lst 5$((i+2)).lst >5$((i+2)).new; done
$