title: Regex with perl one liner
body: <p>I have the following:</p>
  
  <pre><code>XXUM_7_mauve_999119_ser_11.255255
  
  UXUM_566_mauve_999119_ser_11.255255
  
  IXUM_23_mauve_999119_ser_11.255255
  </code></pre>
  
  <p>and my attempt, which did not work, at a perl one liner to extract the first digit is as follows; </p>
  
  <pre><code>perl -pi -e "s/\S+_(\.+)_.+/Number$1/g" *.txt
  </code></pre>
  
  <p>I expected the following results:</p>
  
  <pre><code>Number 007
  Number 566
  Number 023
  </code></pre>
  
  <p>pls help</p>