Using variables in select

I need to process two different selections (attached below). One that
is filtered and one (actually several) that are filtered by
[@Kursart='Bildungsurlaub'] and similar conditions.

Now searching the list I found that I can create a more elegant
soltion by using a variable in this fashion [@Kursart=$aFilter].

What I haven't found is:

        how can I create this in a way that it works also for the
        first variation that doesn't want the filter?

        Is there a way to use pattern matching such as

        $aFilter="*" (which doesn't work!)

Or is this a situation where I need to go for evaluate?
        
Any ideas much appreciated,
Ferdinand Soethe

-------------
Current code

<xsl:for-each select="set:distinct(Kurstext/@Titel|
        Abschnitt[BereichsTitelEinfuegen and BereichsTitelEinfuegen!='immer'
        and
        BereichsTitelEinfuegen!='nurWeb']/Kurstext/@Titel)">
        <xsl:call-template name="UebersichtslistenpunktErzeugenHTML" />
 </xsl:for-each>
 
 <xsl:for-each select="set:distinct(Kurstext[@Kursart='Bildungsurlaub']/@Titel|
        Abschnitt[BereichsTitelEinfuegen and BereichsTitelEinfuegen!='immer'
        and
        BereichsTitelEinfuegen!='nurWeb']/Kurstext[@Kursart='Bildungsurlaub']/@Titel)">
        <xsl:call-template name="UebersichtslistenpunktErzeugenHTML" />
 </xsl:for-each>






--
Ferdinand Soethe