Test for a specified substring within a string.
Integer_Type is_substr (String_Type a, String_Type b)
This function may be used to determine if a contains the
string b. If it does not, the function returns 0; otherwise it
returns the position of the first occurance of b in a.
It is important to remember that the first character of a string
corresponds to a position value of 1.
substr, string_match, str_replace