Q: Where to use XSLT functions like substring-before()?

I've been poring over XML/XSLT references, looking for an example of how
text manipulation functions are used. Everywhere lists the functions, but no
one has them in context of whether they reside in attribute results or a
special element type.

How would I use substring-before() (for example) to generate some text,
something like this?

<xsl:element name="h1" value="substring-before('Mickey Mouse','e')"/>

yeilding:

<h1>Mick</h1>


 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list