<svg xmlns="http://www.w3.org/2000/svg" xmlns:html="http://www.w3.org/1999/xhtml">
  <title>Usage of css var() with when no substitution is provided</title>
  <html:link rel="author" title="Divyansh Mangal" href="mailto:dmangal@microsoft.com"/>
  <html:link rel="match" href="about:blank"/>
  <rect width="var(--length)" height="var(--length)" fill="red"/>
</svg>