http://invest4k4ufq7x2elistx6xihl7nb3fddzmefp5fsjybyybrmlumoqid.onion/bitcoin-changer/index18.html
In this case, this is simple: it checks if the contract's storage at index 2 is used, notices that it is not, and so it sets the storage at index 2 to the value CHARLIE. Suppose this takes 187 gas, so the remaining amount of gas is 1150 - 187 = 963 Add 963 * 0.001 = 0.963 ether back to the sender's account, and return the resulting state.