Replaces tokens in a string with a different token.
replace("A and B and C", "and", "or") -> "A or B or C"
replace("andandand", "and", "or") -> "ororor"
replace(null, "and", "or") -> null
replace("andandand", null, "or") -> "andandand"
replace("andandand", "", "or") -> "andandand"
replace("A and B and C", "and", null) -> "A B C"