Mordechai and Sari had no school and were home the week before Pesach. I gave my (non-Jewish) babysitter, Namie, "prizes" to use as ammo to keep the civilians in order. During the afternoon, I called to check in and Mordechai picked up.
Mordechai: Hi, Mom. I got a prize because I was behaving very well and did good listening. But, Sari - oh, wait. I can't say 'cuz it's lashon ha'ra.
Me (trying to stifle laughter): That's terrific, Mordechai. I'm so glad to hear that you've been behaving so nicely. Good for you.
Mordechai: Yeah, but Mommy I really want to tell you something and I can't because it's lashon ha'ra.
Me: Well, then maybe you shouldn't even though it's hard not to.
Mordechai: Well, acually, maybe it's not lashon ha'ra.
Mordechai: Okay. Let's say Sari got a prize for good listening and I didn't. And let's say she was telling you she got a prize, right? Would it be lashon ha'ra for her to say that I didn't get a prize?
Me: Well, sort of, because then I could figure out that you weren't really doing good listening because you didn't get a prize.
Mordechai (sounding awfully dejected): Oh.
Me (continuing to try to stifle laughter): Mmmm.
Mordechai (brightening considerably): I know what I'll do! I'll tell Namie to tell you.
Mordechai (holding phone away from mouth, talking to Namie): Namie, tell Mom that Sari's not listening.
Mordechai (to me): Okay, Mom. Hold on. Namie wants to tell you something.
Now, how would the Chafetz Chaim have felt about amirah l'akum?