Query string variables are accessible as is in the script, so for example if the URL was:
.../texis/search/feed.xml?q=word
then you can use $q in the script. For example assuming a table structure similar to the Webinator tables the script might be as follows. It is pretty simple, so depending on what else you are looking to do we can point you in the right direction.
<script language=vortex>
<a name=main>
<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="
http://www.w3.org/2005/Atom">
<title>Example Feed</title>
<subtitle>A subtitle.</subtitle>
<sql "select Title, Description, Url from html
where Title\Keywords\Body likep $q">
<entry>
<title>$Title</title>
<link href="$Url" />
<summary>$Description</summary>
</entry>
</sql>
</a>
</script>