For 4.0.x, this should do it:
Code:
<form method="GET" action="search.php">
<input type="hidden" name="simple_search" value="Y" />
<input type="hidden" name="mode" value="search" />
<input type="hidden" name="posted_data[by_title]" value="Y" />
<input type="hidden" name="posted_data[by_shortdescr]" value="Y" />
<input type="hidden" name="posted_data[by_fulldescr]" value="Y" />
<select name="posted_data[substring]">
<option>Text 1</option>
<option>Text 2</option>
<option>Text 3</option>
<option>Text $</option>
</select>
</form>