title: Adding prefix to column names if a pattern in matched
body: <p>The data is as follows :</p>
  
  <pre><code>m2 &lt;- data.frame(a = c(1:5),b = c(1:5),"2016"= c(1:5),"2017"= c(1:5),"2018"= c(1:5),"2019" = c(1:5))
  </code></pre>
  
  <p>I want to add "ABC" before all column name that are years.</p>
  
  <p>2016 should be ABC_2016
  2017 should be ABC_2017
  ...
  2032 should be ABC_2032</p>