Need a command or script

[Dazed_75]

I know I could figure this out, and will tomorrow if no one gives me
the answer in the next hour.  I have a file with many mv xxx yyy
commands and want to make another file with mv yyy xxx commands so
just need to swap the arguments.  I have to go do some things now and
have a meeting tonight so would appreciate a reminder how to do this.
I know it is trivial but just don't remember how right now.  Thanks in
advance.

-- 
Man is the only animal that laughs and weeps, for he is the only
animal that is struck with the difference between what things are and
what they ought to be.
  - William Hazlitt