title: How to convert string to Regex
body: <p>I have this code</p>
  
  <pre><code>reg=~r/(\d{4}.csv)/
  raw="some craxy trashy text blabla 0044.csv"
  Regex.scan(reg,raw, capture: :all_but_first)
  </code></pre>
  
  <p>This returns <code>0044.csv</code>.</p>
  
  <p>However, I need to load the <code>~r/(\d{4}.csv)/</code>  from a database, so I will save it as</p>
  
  <pre><code>"~r/(\d{4}.csv)/"
  </code></pre>
  
  <p>This is a string. When I load it to a variable, it will be a string.</p>
  
  <p>How can I pass it to a <code>Regex.scan</code>?</p>