Problem with `\` 

It seems that the following code will not be correctly transformed:

``` latex
<pre lang="tex">
$\log e^x=x$
</pre>
```

it should be something like:

``` html
<pre class="prettyprint perl">
 <code class="language-tex">
 $\
 log e^
 x=
 x$
</code>
</pre>
```

but it turns out to be 

``` html
<pre>
<code class="language-tex bash">
$log e^x=x$
</code>
</pre>
```

I hope you could have a look!