// ==UserScript==
// @name          MZF SearchBox Show Results as Topics
// @namespace     http://loucypher.wordpress.com/
// @include       http://forums.mozillazine.org/*
// @description	  restrict results to the TOPICs
// ==/UserScript==

var searchForm = document.evaluate('//div[@class="sidebar searchBox"]/form[@action="search.php?mode=results"]',
  document, null, 0, null).iterateNext();

if(!searchForm) return;

var newInput = document.createElement('input');
newInput.name = 'show_results';
newInput.type = 'hidden';
newInput.value = 'topics';

searchForm.appendChild(newInput);