A possible way of expressing Scheme `let`

expressions, such as

```
(let ((x 3) (y 5)) (+ x y))
```

is to use ES6 default parameters:

```
((x = 3, y = 5) => x + y)()
```

It is possible to go one step further by defining an auxiliary `let_`

function as:

```
const let_ = f => f();
```

This allows rewriting the previous function application as:

```
let_((x = 3, y = 5) => x + y);
```

Definitely not the most idiomatic thing to do, though :-)