$ cat nodes.txt
db.blah.org
de.yahoo.com
mail.example.org
www.aol.com
www.example.org
www.freshmeat.net
www.hotdoggie.com.au
www.blah.org
$ cat nodes.txt | perl -ple'$_=join".",reverse split/\./' | sort | perl -ple'$_=join".",reverse split/\./'
www.hotdoggie.com.au
www.aol.com
de.yahoo.com
www.freshmeat.net
db.blah.org
www.blah.org
mail.example.org
www.example.org