The index function searches for one string within another, but without
the wildcard-like behavior of a full regular-expression pattern match.
It returns the position of the first occurrence of SUBSTR in STR at
or after POSITION. If POSITION is omitted, starts searching from the
beginning of the string. POSITION before the beginning of the string
or after its end is treated as if it were the beginning or the end,
respectively. POSITION and the return value are based at 0
(or whatever
you've set the $[
variable to--but don't do that). If the substring
is not found, index returns one less than the base, ordinarily -1
.