With

Unlike the other four scoping functions, with() is not an extension function.

This means you cannot do the following:

"scope".with { ... }

Instead, with() receives the object you want to scope as an argument:

with("scope") {
    println(this.length) // "this" set to the argument of with()
}

And as usual, we can omit this:

with("scope") {
    length
}

Just like run() and let(), you can return any result from with().