title: Why aren't global (dollar-sign $) variables used?
body: <p>I'm hacking around Rails for a year and half now, and I quite enjoy it! :)</p>
  
  <p>In rails, we make a lots of use of local variables, instance variables (like <code>@user_name</code>) and constants defined in initializers (like <code>FILES_UPLOAD_PATH</code>). But why doesn't anyone use global "dollarized" variables ($) like <code>$dynamic_cluster_name</code>? </p>
  
  <p>Is it because of a design flaw? Is it performance related? A security weakness?</p>