**Q:** how can I convert a 2-item list to a dotted pair `cons` cell?

I can convert a 2-item list to a dotted pair with:

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    (let ((list '(1 2)))
      (cons (car list) (cadr list)))        ; => (1 . 2)

I'm blanking: is there a built-in function that does this, or
should I role my own?