Examine $-[0] for the start location of your match. This will not help you if you wanted to use the /g switch in list context so there you have to fudge.

my @offsets;
while ( /B/g ) {
    push @offsets, $-[0];
}
[download]

I'm seeing something I should have expected - for the given string "AABAABAA" and target "AABAA" my @offsets will have one element whose value = 0. I need it to contain 0 and 3...

I know what it's doing, when AABAA is matched, it moves on to the end of the match. What I really need is a sliding window type of match. It didn't dawn on me to explain this until I remembered how this works...

What it's doing:
*AABAA*BAA - matches here
AABAA*BAA regex continues at the asterisk,
but I want it to continure here:
A*ABAABAA
i.e., i guess you could say I need a single-width assertion...
--

Reset pos() to 1 + $-[0] so you're ready for the next character then.

my $ind = -1;
while (($ind = index($string, $substring, $ind+1) >= 0) {
   push @offsets, $ind
}
[download]

   my $mystring = "AABAABBBB";
   my @myarray = split //, $mystring;
   my $ct = 0;
   foreach my $element (@myarray) {
      if ($element eq "B") {
         push(@myoccurrences, $ct);
      }
      $ct++;
   }
[download]

HTH.

Downside of your approach is that you assume the query string will always be one character. diotalevi's approach does not suffer that limitation. Definately works with the test case feloniousMonk presented, but fM refers to 'B' as a query string implying that it could be multiple characters in some cases.

And in fact query string is always <= length of target string...

Thanks for the help everyone, now I have some good suggestions to try out - they're all much better than my own earlier attempts. --