Here's a bizarre way of doing it, taking a hint from my Prolog studies (thanks Ovid!): 
sub match_count {
  my ($string, $pattern) = @_;
  my $n = 0;
  $string =~ /$pattern(?{ $n++ })(?!)/;
  return $n;
}

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Essentially, match successfully, count it, but then fail the match (an empty string can always match, so negating that always fails).

-- Randal L. Schwartz, Perl hacker
Be sure to read my standard disclaimer if this is a reply.

In reply to Re: counting overlapping patterns by merlyn
in thread counting overlapping patterns by Anonymous Monk

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