string literals distinguished through syntax highlighting

Rather than putting strings inside quote marks, and having an escape mechanism, use the ability to highlight syntax to distinguish literals.

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    <pre><font color="#00ffff">#  Perl (version 5)</font>

<font color="#ffff00">my</font> <font color="#00ffff"><b>$phrase</b></font> = <font color="#ff40ff">&quot;Howdy, world!</font><font color="#ffd7d7">\n</font><font color="#ff40ff">&quot;</font>;
<font color="#ffff00">my</font> <font color="#00ffff"><b>$phrase</b></font> = <font color="#000000"><span style="background: #ff40ff">Howdy, world!</span></font>n;
<font color="#ffff00">my</font> <font color="#00ffff"><b>$answer</b></font> = <font color="#ff40ff">42</font>; <font color="#00ffff"># an integer</font>
<font color="#ffff00">my</font> <font color="#00ffff"><b>$pi</b></font> = <font color="#ff40ff">3.14159265</font>; <font color="#00ffff"># a &quot;real&quot; number</font>
<font color="#ffff00">my</font> <font color="#00ffff"><b>$avocados</b></font> = <font color="#ff40ff">6.02e23</font>; <font color="#00ffff"># scientific notation</font>
<font color="#ffff00">my</font> <font color="#00ffff"><b>$pet</b></font> = <font color="#ff40ff">&quot;Camel&quot;</font>; <font color="#00ffff">#...