That selector actually matches up with a bit of Javascript just above it:

$('p.code').each(function (i, c) {
    var code = $(c).find('tt.codetext').text().replace(/\u00a0/g,' ').
+replace(/\s+$/,'');
    var dl   = $(c).find('span.embed-code-dl');
    var pre  = $(
        '<pre class="blockcode"><code>'
        + $('<div/>').text(code).html()
        + '</code></pre>'
    );
    var footer = $('<div style="text-align:right"><small></small></div
+>');
    if (dl.html()) footer.find('small').append(dl.html());
    $(c).after(footer);
    $(c).replaceWith(pre);
});
[download]

The intention of that is to rewrite PerlMonks' code-block markup into a much simpler <pre class="blockcode"><code>...</code></pre>, which the syntax highlighter can then deal with.

However PerlMonks' code-block markup does vary depending on your display settings for code listings. My settings are:

Code Wrapping Off                                  [     ]
Code Wrap Length                                   [     ]
Auto Code Wrapping                                 [ Yes ]
Code Prefix                                        [     ]
Large Code Font                                    [     ]
Don't show embedded d/l links                      [     ]
Show download link on code N lines long or more:   [   4 ]
[download]

If you let me know your settings I can try to make sure pm2.js works better with them.