title: How to Set RUBYOPT on windows to use additional includes
body: <p>I am trying to change my RUBYOPT environment variable.</p>
  
  <p>My aim is to use my own library, which is in C:\ruby_lib, so I do:</p>
  
  <p><code>echo set RUBYOPT="-I C:\ruby_lib\</code></p>
  
  <p>If I try to run my program, which contains only <code>require "dummy.rb"</code> all I get is <code>no such file to load</code>, which should not happen has long as <code>dummy.rb</code> can be found in <code>C:\ruby_lib</code></p>
  
  <p>I am wondering if there is something I am doing wrong when I set the RUBYOPT environment variable.</p>