Programming Perl, 4th Edition

rindex

rindex STR, SUBSTR, POSITION
rindex STR, SUBSTR

This function works just like index except that it returns the position of the last occurrence of SUBSTR in STR (a reverse index). The function returns –1 if SUBSTR is not found. POSITION, if specified, is the rightmost position that may be returned. To work your way through a string backward, say:

$pos = length $string;
while (($pos = rindex $string, $lookfor, $pos) >= 0) {
    say "Found at $pos";
    $pos––;
}

Note that like index, this works by character (codepoint) position, not by grapheme position. To work with strings as sequences of graphemes instead of codepoints, see the index, rindex, and pos methods for the CPAN Unicode :: GCString module.