title: Newly installed Ruby gems not showing up in $LOAD_PATH
body: <p>I'm using MacPorts in order to manage my Ruby/Rails/Gems installations. Recently after doing a <code>gem install wirble</code>, wirble fails to load when I start an instance of irb. Here's the output:</p>
  
  <pre><code>$ irb --simple-prompt
  Couldn't load Wirble: no such file to load -- wirble
  </code></pre>
  
  <p>The Wirble gem doesn't show up in my $LOAD_PATH:</p>
  
  <pre><code>&gt;&gt; puts $:
  /opt/local/lib/ruby1.9/gems/1.9.1/gems/actionmailer-2.3.5/lib
  /opt/local/lib/ruby1.9/gems/1.9.1/gems/actionpack-2.3.5/lib
  /opt/local/lib/ruby1.9/gems/1.9.1/gems/activerecord-2.3.5/lib
  /opt/local/lib/ruby1.9/gems/1.9.1/gems/activeresource-2.3.5/lib
  /opt/local/lib/ruby1.9/gems/1.9.1/gems/activesupport-2.3.5/lib
  /opt/local/lib/ruby1.9/gems/1.9.1/gems/mysql-2.8.1/lib
  /opt/local/lib/ruby1.9/gems/1.9.1/gems/mysql-2.8.1/ext
  /opt/local/lib/ruby1.9/gems/1.9.1/gems/mysql-2.8.1/bin
  /opt/local/lib/ruby1.9/gems/1.9.1/gems/rack-1.0.1/bin
  /opt/local/lib/ruby1.9/gems/1.9.1/gems/rack-1.0.1/lib
  /opt/local/lib/ruby1.9/gems/1.9.1/gems/rails-2.3.5/bin
  /opt/local/lib/ruby1.9/gems/1.9.1/gems/rails-2.3.5/lib
  /opt/local/lib/ruby1.9/gems/1.9.1/gems/rake-0.8.7/bin
  /opt/local/lib/ruby1.9/gems/1.9.1/gems/rake-0.8.7/lib
  /opt/local/lib/ruby1.9/gems/1.9.1/gems/rubygems-update-1.3.7/hide_lib_for_update
  /opt/local/lib/ruby1.9/gems/1.9.1/gems/rubygems-update-1.3.7/bin
  /opt/local/lib/ruby1.9/site_ruby/1.9.1
  /opt/local/lib/ruby1.9/site_ruby/1.9.1/i386-darwin10
  /opt/local/lib/ruby1.9/site_ruby
  /opt/local/lib/ruby1.9/vendor_ruby/1.9.1
  /opt/local/lib/ruby1.9/vendor_ruby/1.9.1/i386-darwin10
  /opt/local/lib/ruby1.9/vendor_ruby
  /opt/local/lib/ruby1.9/1.9.1
  /opt/local/lib/ruby1.9/1.9.1/i386-darwin10
  .
  =&gt; nil
  &gt;&gt; 
  </code></pre>
  
  <p>The gem is definitely installed:</p>
  
  <pre><code>$ gem list |grep -i wirble
  wirble (0.1.3)
  </code></pre>
  
  <p>It is located in <code>/opt/local/lib/ruby/gems/1.9.1/gems/wirble-0.1.3/</code></p>
  
  <p>How do I get this and future gems I installed appended to my $LOAD_PATH?</p>