Using contains with more than one string - XSLT2.0

I've done some googling on this but nothing seems quite to match what I want
to do.

At the top of my style sheet I have this:

   <xsl:variable name="target" select="'Photo'"/>

Then later I do this to find all titles with that string in them:

   <xsl:for-each
select="//dsc//unittitle[contains(normalize-space(.),$target)]">

So far so good, works great.  The problem comes when I want to tell the
contains function to match on any one of several strings, e.g. Photo or Neg or
Film.  So far I have tried the following but none of them work:

   <xsl:variable name="target" select="'Photo|Neg'"/>
   <xsl:variable name="target" select="'Photo'|'Neg'"/>
   <xsl:variable name="target" select="'Photo' or 'Neg'"/>
   <xsl:variable name="target" select="'Photo Neg'"/>

If I must, I can stick the or'ed terms directly in the contains function
rather than using a variable, but when I tried a few variations on that, they
didn't work either.

Thanks

Michele
+++++++++++++++
Michele Combs
Lead Archivist
Special Collections Research Center
Syracuse University Libraries
315-443-2081
mrrothen@xxxxxxx
scrc.syr.edu