Since we already know recursion we can play a little bit more, now consider we have a list of element, and we want to replace that
element with another one, but at the same time remember the old one.
For example if we have [1,2,3] and we replace the second element with
"hi", it should be [1, #{current => "hi", old => 2}]. And if we
call that function with [1, #{current => 10, old => 0}, 3] replacing the
second element with "hi" the result should be [1, #{current => "hi", old => 10}, 3].
The function should be insert_element_at:insert/3. A sample call of the
previous example could be insert([1,2,3], 2, "hi"). If you are stuck or
want to compare check our solution.