I'm having some problems passing parameters into XSLT with ruby. The 
following script, based on the example in the docs

----- run.rb

#!/usr/bin/ruby 

require 'rubygems'

require 'xml'
require 'xslt'

# Create a new XSL Transform
stylesheet_doc = LibXML::XML::Document.file('browse.xsl')
stylesheet = LibXSLT::XSLT::Stylesheet.new(stylesheet_doc)

# Transform a xml document
xml_doc = LibXML::XML::Document.file('page.xml')
result = stylesheet.apply(xml_doc, {:root => "ROOT", :back => "BACK"})

puts result

Processes these two files

----- page.xml

<?xml version="1.0" encoding="UTF-8"?>
<doc />

----- browse.xsl

<?xml version="1.0"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
	<xsl:output method="xml" indent="yes" />

  <xsl:param name="root" />
  <xsl:param name="back" />
  
  <xsl:template match="/">
	  <doc>
		  <p>This is the value of root is <xsl:value-of select="$root" /></p>
		  <p>This is the value of back is <xsl:value-of select="$back" /></p>
	</doc>
  </xsl:template>
</xsl:stylesheet>

When run produces the following output:

$ ./run.rb
<?xml version="1.0"?>
<doc>
  <p>This is the value of root is </p>
  <p>This is the value of back is </p>
</doc>
$

As you can see the parameters 'root' and 'back' have not been filled in. When I run the data with xsltproc it works ok which would suggest that it is not a problem with the data or the stylesheet.

$ xsltproc --stringparam root 'ROOT' --stringparam back 'BACK' browse.xsl page.xml
<?xml version="1.0"?>
<doc>
  <p>This is the value of root is ROOT</p>
  <p>This is the value of back is BACK</p>
</doc>
$

Here is what I have:

$ ruby -v
ruby 1.8.6 (2008-03-03 patchlevel 114) [universal-darwin9.0]
$ gem list

*** LOCAL GEMS ***

actionmailer (2.1.2)
actionpack (2.1.2, 1.13.6)
actionwebservice (1.2.6)
activerecord (2.1.2, 1.15.6)
activesupport (2.1.2, 1.4.4)
acts_as_ferret (0.4.3)
capistrano (2.0.0)
cgi_multipart_eof_fix (2.5.0)
daemons (1.0.10)
dnssd (0.7.0)
fastthread (1.0.1)
fcgi (0.8.7)
ferret (0.11.6)
gem_plugin (0.2.3)
highline (1.5.0)
hpricot (0.6.164)
json (1.1.3)
libxml-ruby (0.8.3)
libxslt-ruby (0.8.2)
mongrel (1.1.5)
needle (1.3.0)
net-sftp (2.0.1)
net-ssh (2.0.4)
rails (2.1.2)
rake (0.8.3)
RedCloth (3.0.4)
ruby-openid (2.1.2)
ruby-yadis (0.3.4)
rubynode (0.1.5)
sqlite3-ruby (1.2.4)
termios (0.9.4)