title: Ruby, check if string is all valid hex characters?
body: <p>I have to check if a 4 character string is all valid hex, I found another question which demonstrates exactly what I want to do but it's Java: <a href="https://stackoverflow.com/questions/5317320/regex-to-check-string-contains-only-hex-characters">Regex to check string contains only Hex characters</a></p>
  
  <p>How can I accomplish this?</p>
  
  <p>I read the ruby docs for Regular expressions, but I don't understand how to return a true or false based on this match?</p>