title: Interpolating a string into a regex
body: <p>I need to substitute the value of a string into my regular expression in Ruby. Is there an easy way to do this? For example:</p>
  
  <pre><code>foo = "0.0.0.0"
  goo = "here is some other stuff 0.0.0.0" 
  if goo =~ /value of foo here dynamically/
    puts "success!"
  end
  </code></pre>