title: How to match string between two delimiters and append a string after
body: <p>I have a file with the contents like below:</p>
  
  <pre><code>[idx1]
  path1 = $test/idx1/test
  path2 = $test/idx1/test
  path3 = $test/idx1/test
  
  [idx2]
  path1 = $test/idx2/test
  path2 = $test/idx2/test
  path3 = $test/idx2/test
  </code></pre>
  
  <p>Is there a way to match all strings like idx1, idx2 between the delimiters and append a string after each match.</p>
  
  <pre><code>[idx1_string]
  path1 = $test/idx1_string/test
  path2 = $test/idx1_string/test
  path3 = $test/idx1_string/test
  
  [idx2]
  path1 = $test/idx2_string/test
  path2 = $test/idx2_string/test
  path3 = $test/idx2_string/test
  </code></pre>