class X {
    fun doStuff(name: String) = println("hello, $name")
}

class X.Y {
    operator fun invoke( body : X.() -> Unit ) { doStuff("max"); body(); }
}

fun main() : X.() -> Unit = {
    doStuff("peter")
    Y {
        doStuff("franz")
    }
}

/** output would be:
 *    hello peter
 *    hello max
 *    hello franz
 */