title: using sed command in substitution
body: <p>When I use this command</p>
  
  <pre><code>echo jones:Adrian W. Jones/OSD211/555-0123 | sed -e 's=^([^:]*):[^/]*/([^/]*)/.*$=\1:\2='
  </code></pre>
  
  <p>I got: <strong>sed: command garbled: s=^([^:]<em>):[^/]</em>/([^/]<em>)/.</em>$=\1:\2=</strong></p>
  
  <p>but when I use this one:</p>
  
  <pre><code>echo jones:Adrian W. Jones/OSD211/555-0123 | sed -e 's=^\([^:]*\):[^/]*/\([^/]*\)/.*$=\1:\2='
  </code></pre>
  
  <p>I got: <strong>jones:OSD211</strong></p>
  
  <p>Why should I escape the <code>(</code> in sed?</p>