I believe find2perl# ls clears up why it works(ordoesnt) the way it does (it does dils only), and simultaneously tells you the non-portable solution (use -exec)

Also, find2perl finds File::Finder which also does dils only, but if you view the source of sub ls and sub _ls you can see it is written clear enough so that you can simulate -ltr as well

http://perldoc.perl.org/perlfaq4.html#How-do-I-sort-an-array-by-%28anything%29%3f