When-statement as expression

Like if, when can also be used as an expression:

val greeting = when (x) {
    "English" -> "How are you?"
    "German" -> "Wie geht es dir?"
    else -> "I don't know that language yet :("
}
print(greeting)

To be used as an expression, the when-statement must be exhaustive, i.e. either have an else branch or cover all possibilities with the branches in another way.