The $MT template variable causes Flash to insert all the text from the current SWF file as a comment in the HTML code. This is useful for indexing the content of a SWF file and making it visible to search engines.

The $MU template variable makes Flash generate a list of the URLs that actions in the current SWF file refer to and insert the list at the current location as a comment. This action lets link verification tools detect and verify the links in the SWF file.