inline call to external process

Is it possible to invoke an external process from within xml,
like a script (shell, perl, whatever) that returns xml markup?
This returned code is then parsed by the xslt processor inplace 
just like the static code.

-- 
Eric Smith - currently using xalan and xsltproc 
- what a difference speed makes - and fop on linux

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