title: Apache - set environment variable from proxy response header
body: <p>I am proxying apache requests to s3 and I want to rewrite the response header into a new crafted header</p>
  
  <p>this is my configuration:</p>
  
  <pre><code>SetEnvIf x-amz-meta-link "(.*)" DYN_CSS=$0
  Header set Link "&lt;/static_assets/stylesheets/application-%{DYN_CSS}e.css&gt;; rel=preload; as=stylesheet" env=DYN_CSS
  </code></pre>
  
  <p>s3 Header is configured to be x-amz-meta-link: css</p>
  
  <p>I am expecting the header in the final response to be</p>
  
  <pre><code> &lt;/static_assets/stylesheets/application-css.css&gt;; rel=preloadas=stylesheet" 
  </code></pre>
  
  <p>but what I get is (empty var)</p>
  
  <pre><code>&lt;/static_assets/stylesheets/application-.css&gt;; 
  </code></pre>