title: Generating regex-based string with RandExp
body: <p>I need to generate a string based on regex which would result random letters and numbers, 4 dashes at random places in 36-character string.</p>
  
  <p>Example:</p>
  
  <p><code>123A5678-01B3C5F7-901R345-789F1-3456</code></p>
  
  <p>I've figured out a regex that seems to validate given string well:</p>
  
  <p><code>(?=.{36}$)([0-9A-Z]+-){4}([0-9A-Z])+</code></p>
  
  <p>...but using the same for generating string in RandExp ends  up in a mess. It generates 36-character string and adds 5 random-length groups: </p>
  
  <p><code>new RandExp(/(?=.{36}$)([0-9A-Z]+-){4}([0-9A-Z])+/).gen()</code></p>
  
  <p><code>M78QMOC6OGIF5OAJAJCG68CQWJGT5FX43CTKZ9CS9GXWLEKUKZMG602U5HPR4CEKO7OIX45CMLB7DS5RHZBI8KE8HGO9ET6OWS9A-PQSHN9E36KIMW328A1L0BHXCFOJVCD2ZT11-KD03XTZ375WP7CR7YSF4CTSX-0FBJ3MZ4RNDLA5UZOHI5QWVY66PTUDDRCG-OH4F688VM1</code> </p>
  
  <p>Should I just settle for fixed-width groups for my string using something like:</p>
  
  <p><code>([0-9A-Z]{6}-){4}[0-9A-Z]{8}</code></p>
  
  <p>... or is there any way I could improve the original regex?</p>