conditional inlcudes -is it possible?

Hello,
This is our situation. We have a global xsl that
ensures that all our webpages have a certain content.
We are trying to make the inclusion of local xsl
stylesheets conditional based on where the request is
coming from so this brings out two questions:
a) is there a function like say HTTP_REFERER (in php)
that tells you the page/uri that requested the page
and,
b) is there a way to include different XSL stylesheets
into one XSL stylesheet based on the information from
'a'.

I do know that multiple includes are possible, but
when I tried this, as a first step, this also did not
work:

<xsl:variable
name="location">http://theurl</xsl:variable>
</xsl:include href="$location" />

This came out with the error that no stylesheet has
been speficied. This part would be necessary if 'a'
and 'b' could be done.

Thanks for your help in advance,
Vedu


__________________________________________________
Do you Yahoo!?
New DSL Internet Access from SBC & Yahoo!
http://sbc.yahoo.com

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