Snippet call within FeedX preset?

I’m trying to use regex to change Google headline links into XHTML 1.1 valid references ( replacing "&" with "&" ).

So instead of the standard Atom preset for entry.tpl of:

<a href="[+LINK.HREF+]">[+TITLE+]</a>

I tried to change it to call another snippet:

<a href="[[atomEntry]]">[+TITLE+]</a>

but all I get is a parse error for an extra "["

Has anyone succeeded at something like this?