title: Remove duplicate lines with a twist gnuwin32
body: <p>Okay so I want remove duplicate lines but it's a bit more complicated than that.. </p>
  
  <p>I have a file named users.txt, example of file is:</p>
  
  <pre><code>users:email@email.com
  users1:email@email.com
  </code></pre>
  
  <p>Now due to a bug in my system people were able to register with the same email as someone else, so I want to remove if lines have the same email more than once, example of issue:</p>
  
  <pre><code>user:display:email@email.com
  user2:email@email.com
  user3:email@email.com
  user4:email@email.com
  </code></pre>
  
  <p>Notice how user, user2, user3, user4 all have the same email.. well I want to remove user2, user3, user4 but keep user.. or vice versa ( first one to be picked up by request ) remove any other lines containing same email..</p>
  
  <p>so if</p>
  
  <pre><code>email@email.com is in 20 lines remove 19
  spam@spam.com is in 555 lines remove 554
  </code></pre>
  
  <p>and so fourth.. </p>