I don't know much about XSLT2 or Saxon's extensions, but the errors from your second case here seem fairly simple to fix:

<xsl:import href="f/func-exp.xsl"
use-when="system-property('System.getenv(&quot;f&quot;)')= 'true'"  />

Putting the quotes around f made that attribute into invalid XML. Does that work?

~ Scott

-----Original Message-----
From: Dave Pawson [mailto:davep@xxxxxxxxxxxxx] 
Sent: Saturday, March 13, 2010 5:00 AM
To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
Subject: Re:  import, xslt 2.1

Tried using use-when with an environmental variable.

<xsl:import href="f/func-exp.xsl"
use-when="system-property('System.getenv('f')')= 'true'"  />

Error on line 14 of fxslexamples.xsl:
   XPST0003: Error in use-when expression. XPath syntax error at char 32 
on line 14 in
   {...-property('System.getenv('f...}:
     expected ")", found name "f"
Failed to compile stylesheet. 1 error detected.

Changed the quotes to
<xsl:import href="f/func-exp.xsl"
use-when="system-property('System.getenv("f")')= 'true'"  />
and get

Error on line 14 column 43 of fxslexamples.xsl:
   SXXP0003: Error reported by XML parser: Element type "xsl:import" 
must be followed by
   either attribute specifications, ">" or "/>".
Failed to compile stylesheet. 1 error detected.

Looks like it can't be done.


regards

-- 
Dave Pawson
XSLT XSL-FO FAQ.
http://www.dpawson.co.uk