my $i = index reverse($phrase),$what;
[download]

use strict;
print join(",",rindexes("hello world , kill bill","ll"));

sub rindexes {
    my $s = reverse shift;
    my $what = reverse shift;
    my @indexes;
    my $old = 0;
    while ((my $i = index $s,$what,$old) > -1) {
        push @indexes, length($s) - $i - length($what) +1;
        $old = $i+1;
    }
    @indexes;
}
[download]