title: Match all elements with n occurrences
body: <p>I want to select the same element with exact n occurrences.</p>
  <p>Match letters that repeats exact 3 times in this String: <strong>&quot;aaaaabbbcccccccccdddee&quot;</strong></p>
  <p>this should return <strong>&quot;bbb&quot;</strong> and <strong>&quot;ddd&quot;</strong></p>
  <p>If I define what I should match like &quot;b{3}&quot; or &quot;d{3}&quot;, this would be easier, but I want to match all elements</p>
  <p>I've tried and the closest I came up is this regex: <strong>(.)\1{2}(?!\1)</strong>
  Which returns <strong>&quot;aaa&quot;</strong>, <strong>&quot;bbb&quot;</strong>, <strong>&quot;ccc&quot;</strong>, <strong>&quot;ddd&quot;</strong></p>
  <p>And I can't add negative lookbehind, because of &quot;non-fixed width&quot; <strong>(?&lt;!\1)</strong></p>