Unable to use XSLTAddRule

[zigazou@xxxxxxx]

Hi there !

I tried to use the XSLTAddRule (Apache2). The following two lines :
XSLTAddRule "/srv/phpx/doc/mozilla.xsl" "$HEADER[User-Agent] =~ '/Mozilla/'"
XSLTAddRule "/srv/phpx/doc/opera.xsl" "$HEADER[User-Agent] =~ '/Opera/'"

give me the following errors :

[Mon Sep 19 21:07:34 2005] [error] [client 10.0.0.1] mod_xslt: can't compile 
regular expression: Mozilla, unknown option bit(s) set
[Mon Sep 19 21:07:34 2005] [error] [client 10.0.0.1] mod_xslt: can't compile 
regular expression: Opera, unknown option bit(s) set

The following line doesn't generate any error and works as it should :
XSLTAddRule "/srv/phpx/doc/mozilla.xsl" "$HEADER[User-Agent] = 'Mozilla/5.0 
(X11; U; Linux i686; fr-FR; rv:1.7.10) Gecko/20050717 Firefox/1.0.6'"

It did exactly the same thing with these versions under Apache2 :
mod-xslt 1.3.8 2004112100
mod-xslt 1.3.9 2005072700

Any idea where it might come ?