this purpose is the keyword type. A
keyword begins with a colon, and then contains 0 or more alphanumeric or a few
other common characters. For example, <code class="mendoza-code">:hello</code>, <code class="mendoza-code">:my-name</code>, <code class="mendoza-code">::</code>,
and <code class="mendoza-code">:ABC123_-*&amp;^%$</code> are all keywords.
</p>
<p>Keywords, symbols, and strings all behave similarly and can be used as keys for
tables and structs.  Symbols and keywords are optimized for fast equalit