S9 LIB  (string-find-last string1 string2)          ==>  string | #f
        (string-ci-find-last string1 string2)       ==>  string | #f
        (string-find-last-word string1 string2)     ==>  string | #f
        (string-ci-find-last-word string1 string2)  ==>  string | #f

        (load-from-library "string-find-last.scm")

Find the last occurrence of a small string STRING1 in a large
string STRING2. Return the last substring of STRING2 beginning
with STRING1. When STRING2 does not contain STRING1, return #F.
STRING-CI-FIND-LAST performs the same function, but ignores case.

STRING-FIND-LAST-WORD (STRING-CI-FIND-LAST-WORD) differs from
STRING-FIND-LAST (STRING-CI-FIND-LAST) in that is matches only
full words, where a full word is a subsequence of characters that
is delimited on both sides by one of the following:

        - the beginning of the string;
        - the end of the string;
        - a non-alphabetic character.

(string-find-last "a" "aaaaa")        ==>  "a"
(string-ci-find-last "A" "ab ac")     ==>  "ac"
(string-find-last "ax" "ab ac")       ==>  #f
(string-find-last-word "a" "ab a c")  ==>  "a c"
(string-find-last-word "a" "ab ac")   ==>  #f
