I'd do this on the client side with a little onclick to show the select tag. I do this a lot and it has nothing to do with Perl.
<input type="radio" value="1" name="foobar" />
<input type="radio" value="2" name="foobar" onclick="document.getEleme
+ntById('menu').style.visibility='visible'" />
<select name="somechoice" id="menu" style="visibility: hidden">
etc.
You could use display: none and display: block, the difference being display will collapse the space on the page where the menu would go.
—Brad
"The important work of moving the world forward does not wait to be done by perfect men." George Eliot