p.even, p.odd {
    margin: 0;
    padding: 0.2em;
}
p.odd {
    background-color: #ccc;
}

##</code><code>##

<p class="even">#!/usr/bin/perl</p>
<p class="odd">use&#160;strict;</p>
<p class="even">use&#160;warnings;</p>
<p class="odd"></p>
<p class="even">BEGIN&#160;{</p>
<p class="odd">&#160;&#160;&#160;&#160;$|&#160;=&#160;1;</p>
<p class="even">}</p>
...