title: Insert text in the middle of a text file after the first occurence of a search string using sed
body: <p>I am wondering if it is possible to insert some text in the middle of a text file after the first occurrence of a search string using GNU sed.</p>
  
  <p>So for example, if the search string is "Hello",  I would like to insert a string right after the first occurrence of "Hello" on a new line</p>
  
  <pre><code>Hello John, How are you?
  ....
  ....
  ....
  Hello Mary, How are you doing? 
  </code></pre>
  
  <p>The string would be entered right after "Hello John, How are you?" on a new line</p>
  
  <p>Thanks,</p>