sub countOverlappingMatches
{
  my $stringRef = shift;  #Likely to be huge, don't make a copy
  my $patternRef = shift;

  my $count =()= $$stringRef =~ /(?=$$patternRef)/g;
  return $count;
}

print countOverlappingMatches(\'abrabrabrabra', \'rabra');  # 3