Returns the position of the last occurrence of a string,
needle, in the receiving buffer. (See also
Section 5.4.15.25, “pos”.) It returns
0 if
needle is the null string or not found. By default, the search starts at the last character of the receiving buffer and scans backward to the beginning of the string. You can override this by specifying
start, the point at which the backward scan starts and
length, the range of characters to scan. The
start must be a positive whole number and defaults to
receiving_buffer~length if larger than that value or omitted. The
length must be a non-negative whole number and defaults to
start. The search is performed using caseless comparisons.
