title: How to use the {n} syntax of regex with CMake
body: <p>I have this string "2017-03-05-02-10-10_78205" and I want to match it with this pattern <code>[0-9]{4}(-[0-9]{2}){5}_[0-9]+</code> but it doesn't work on CMake. See this example in CMake :</p>
  
  <pre><code>set(stuff "2017-03-05-02-10-10_78205")
  if( "${stuff}" MATCHES "[0-9]{4}(-[0-9]{2}){5}_[0-9]+")
    message("Hello")
  endif()
  </code></pre>
  
  <p>CMake doesn't seem to support the syntax <code>{n}</code>. Obviously, I solved my problem with that pattern <code>[0-9-]+_[0-9]+</code></p>
  
  <p>Nevertheless, I would like to know if I'm doing something wrong with the syntax <code>{n}</code>. Is it supported by CMake ? If not, how to define a specific number of repetition with CMake ?</p>
  
  <p>I'm using an old CMake version (2.8.11.2).</p>