Peru travel tip - counterfeit money
Counterfeit money is very common in Peru. Even down to a 5-sol coin, you will find counterfeits. Of course, that 2-dollar loss isn't going to hurt too bad, but it sure will hurt if you get stuck with a 100-sol counterfeit bill.
One of the common scams you need to recognize and avoid is this:
You pay with a soft-money bill. The person lifts it up to the light, rubs the surface, checks the lines, etc; all normal and typical.
The difference is that the person hands it back to you saying, I can't take/change this, it is false.
Sure enough, when you look at it, it is false.
What you didn't see was that the person, somewhere along the line, has grabbed your good bill and substituted a false one. Now, he has the good one, and you are stuck.
What are you going to do? Nothing. There is no way to prove that he gave you the false bill.
Therefore, if you are paranoid and/or are going to be changing a lot of bigger bills and you have the chance, take photos of them first.
That is about the only way you could prove a sleight of hand.
The best way is to avoid the situation entirely, either holding onto you bill or watching like an eagle to see what is going on.