I needed to reverse the order of blank-separated words. `tac` comes to mind and has an `-s`-option.

So I tried

 $ echo -e A B C D E F | tac -s' ';echo
 F
 E D C B A 
 $ echo -e A B C D E F | tac -s' ' | tr ' ' '-';echo
 F
 E-D-C-B-A-
 $

where the final `echo` is to have the next prompt on a separate line and the `tr ' ' '-'` is to see any invisible blanks at the end of the output lines.

What irritates me is the newline after the "F" in the output.

Looks like a bug to me, is it?

While writing this question and looking at the suggestions for similar questions (a **very good** feature) I saw https://unix.stackexchange.com/q/598611/268339 and learned about rev, which is exactly what I wanted.

Still, for `tac`, is it a bug or a feature?