title: Eclipse Environment Variable Error
body: <p>I'm using Eclipse Mars, and am running an application with some VM arguments and have environment variables defined on the run configuration</p>
  
  <p><code>TOMCAT_HOME c:\tomcat</code></p>
  
  <p>I have the following in the Environment tab VM arguments:
  <code>-Dcatalina.home=${TOMCAT_HOME}</code></p>
  
  <p>I get the following error:</p>
  
  <p><code>Reference to undefined variable TOMCAT_HOME</code></p>
  
  <p>How come I am specifying the variable in the run configuration but it is not working as a VM arg?</p>
  
  <p>Edit:</p>
  
  <p>Turns out that the answer is that you need to add a <strong>Classpath Variable</strong> from <strong>Window->Preferences</strong> menu.  That's confusing.</p>