title: regex, match a substring within a string
body: <p>I want to a capture a string with this regex:</p>
  
  <pre><code>^([\d]_[a-z|A-Z]+_test)$
  </code></pre>
  
  <p>So it would capture something like: <code>1_mytest_test</code></p>
  
  <p>However, if the string is within another string like:</p>
  
  <pre><code>results.1_mytest_test.=fail, more info
  </code></pre>
  
  <p>There is no match.</p>
  
  <p>I thought the <code>^</code> and <code>$</code> would demarcate the beginning and end of the string that I am looking for, right?</p>