<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG June 1999//EN" 
  "http://www.w3.org/Graphics/SVG/svg-19990625.dtd">
<svg width="4in" height="3in">
  <defs>
    <filter id="UseParams">
      <REImageTurbulence base-frequency="{$freq}" num-octaves="{$num}" />
    </filter>
  </defs>
  <rect x="70" y="10" width="40" height="40"
        style="fill:red; 
               filter:url(#UseParams);
               filter-params:freq(20) num(10)" />
</svg>
