To get the ball rolling, here's a snippet from Smarty. I've never used it before, so this is just ripped from their documentation; feel free to edit this post if you have a better sample.
{* I am a Smarty comment, I don't exist in the compiled output *}
<html>
<head>
<title>{$title}</title>
</head>
<body>
{* another single line smarty comment *}
<!-- HTML comment that is sent to the browser -->
{* this multiline smarty
comment is
not sent to browser
*}
{*********************************************************
Multi line comment block with credits block
@ author: [email protected]
@ maintainer: [email protected]
@ para: var that sets block style
@ css: the style output
**********************************************************}
{* The header file with the main logo and stuff *}
{include file='header.tpl'}
{* Dev note: the $includeFile var is assigned in foo.php script *}
<!-- Displays main content block -->
{include file=$includeFile}
{* this <select> block is redundant *}
{*
<select name="company">
{html_options options=$vals selected=$selected_id}
</select>
*}
<!-- Show header from affiliate is disabled -->
{* $affiliate|upper *}
{* you cannot nest comments *}
{*
<select name="company">
{* <option value="0">-- none -- </option> *}
{html_options options=$vals selected=$selected_id}
</select>
*}
{* cvs tag for a template, below the 36 SHOULD be an american currency
. however its converted in cvs.. *}
{* $Id: Exp $ *}
{* $Id: *}
</body>
</html>