# Objective
I can write a recursive function that works on a string.
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# LetterSwap
`(swap "wallaby" "a" "x")`
`=> "wxllxby"`
`swap: word original replace -> string`
Change the letter `original` to the letter `replace` in the `word`.
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# No Mistakes
`no-mistake: string(word) -> string`
Remove every appearance of "mistake" inside the given word.