That solved it. Thanks!

From: David Carlisle d.p.carlisle@xxxxxxxxx
[mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx]
Sent: Thursday, November 05, 2015 11:05 AM
To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
Subject: Re:  Trouble passing XSL function a parameter

regex is an AVT attribute so:

        <xsl:analyze-string select="$data" regex="{$searchstring}" flags="i">

David
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