Instead of doing a big writeup, here are examples from
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Replace("alphabet", "bet", "hydro") would return "alphahydro"
Replace ("alphabet", "a", "e") would return "elphebet"
Replace("alphabet", "a", "e", 2) would return "lphebet"
Replace("alphabet", "a", "e", 1, 1) would return "elphabet"
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