title: Merge dataframe with a key value that is contained within a string in a separate dataframe
body: <pre><code>employee &lt;- c('John','Peter', 'Gynn', 'Jolie', 'Hope', 'Sue', 'Jane', 'Sarah')
  salary &lt;- c('VT020', 'VT126', 'VT027', 'VT667', 'VC120', 'VT000', 'VA120', 'VA020')
  
  emp &lt;- data.frame(employee, salary)
  
  
  benefit &lt;- c('Health', 'Time', 'Bonus')
  benefit_id &lt;- c('VT020 VT126 VT667 VA020', 'VT667', 'VT126 VT667 VT000')
  
  ben &lt;- data.frame(benefit, benefit_id)
  
  </code></pre>
  <p>Above we have to dataframes, one contains names and a unique ID, the other contains a category and a list of unique IDs.</p>
  <p>What is the most efficient way to merge the <code>ben</code> dataframe with the <code>emp</code> dataframe such that we get the appropriate benefit assigned to each employee?</p>