Posn()
Description
FUNCTION: posn(<string>, <pattern>, <n>)
Returns the position of the Nth occurrence of a pattern within a string. This generalizes pos(), which returns only the position of the first occurrence.
Examples
> say posn(abcabc, a, 1)
You say, “1”
> say posn(abcabc, a, 2)
You say, “4”