While discussing other methods that avoided regular expressions in the CB with bobf and nothingmuch, I mentioned an unpack/hash solution. nothinmuch asked to see it, so here is a highly untested alternative. 
#!/usr/bin/perl
use strict;
use warnings;

print str_count('ABAABAAAA', 'AA'), "\n";

sub str_count {
    my ($str, $pat) = @_;
    my %substr;
    my ($p_len, $s_len) = (length $pat, length $str);

    my $template = ("A$p_len" . 'X' . ($p_len - 1)) x ($s_len - $p_len
+ + 1);
    $substr{$_}++ for unpack $template, $str;
    return $substr{$pat};
}

[download]

Cheers - L~R

In reply to Re^2: counting overlapping patterns by Limbic~Region
in thread counting overlapping patterns by Anonymous Monk

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