I believe so Catherine. 

If you mean "be careful what you wish for. Did you know, here in India, people believe that if you have black spots on your tongue, its called black tongue. So

you have to watch what you say and wish for or else it will come true. So these unique people must strictly follow certain rules like "Cursing is a big No-No". Think long and hard before you say anything.

I dont know if thats so in other cultures. lol. So, like you said...think long and hard what benefits you wish for, whether you have a black tongue or not.