str, str StrSplit(str s, str separator)

Finds the first instance of separator and returns text before and after the separator. If the separator is not found, returns (s, "").

StrSplit("abcdefghi", "def");
r1 -> "abc"
r2 -> "ghi"

StrSplit("defghi", "def"); // Nothing before separtor
r1 -> "";
r2 -> "ghi";

StrSplit("abcdef", "def"); // Nothing after separator
r1 -> "abc";
r2 -> "";

StrSplit("abc", "def"); // Not found
r1 -> "abc";
r2 -> "";