title: concat string to beginning of another string
body: <p>Is there a function that allows me to concatenate a string to the beginning of another string?</p>
  
  <p>For example, if I have</p>
  
  <pre><code>str1 = "world!";
  str2 = "Hello, ";
  </code></pre>
  
  <p>Is there some way to combine those strings into one string that contains "Hello, world!"?</p>