title: Expanding regex metachars into character classes
body: <p><code>\d</code> can be expanded to <code>[0-9]</code> and <code>\w</code> can be expanded to <code>[0-9a-zA-Z_]</code>. Is it possible to expand <code>.</code>, <code>$</code>, and <code>^</code>? If so, what would those look like in a character class?</p>