title: Greenspunning: Most impressive extension of a language you have made and whether it was worth it
body: <p><a href="http://en.wikipedia.org/wiki/Greenspun%27s_Tenth_Rule" rel="nofollow noreferrer">Greenspunning</a>. We've all had occasion to hack around a language's missing features to get what we need. Implementing pseudo-monadic patterns in Java,  Y Combinators in Javascript, variable immutability in C... </p>
  
  <p>What do you consider your most impressive workaround in search of greater functionality? In hindsight, was it worth the hack? Even better: did it, like Ruby's <a href="http://weblog.raganwald.com/2007/10/stringtoproc.html" rel="nofollow noreferrer">string#to_proc</a>, become an accepted feature of a later version of the language?</p>