title: Make regex more specific - only select "VB", not variations ("VB%")
body: <p>Consider the following string and regex:</p>
  
  <pre><code>$string= "just/RB convinced/VBN closing/VBG 10dma/NN need/VBN see/VB";
  echo preg_replace("/(\w+)\/(JJ|RB|VB)/", "not$1/$2", $tweet);
  </code></pre>
  
  <p>I want to concatenate "not" to every word ending in /JJ, /RB or /VB. However, the regex also captures variations on /VB: /VBN and /VBG. The output is</p>
  
  <pre><code>notjust/RB notconvinced/VBN notclosing/VBG 10dma/NN notneed/VBN notsee/VB
  </code></pre>
  
  <p>However, the expected output is:</p>
  
  <pre><code>notjust/RB convinced/VBN closing/VBG 10dma/NN need/VBN notsee/VB
  </code></pre>
  
  <p>How can I stop the regex from grabbing there variations?</p>