[xsl] XSLT processor and substring-after

["N Zhou" <zhou_naijun@xxxxxxxxxxx>]

Hi,

I'm using XML::XSLT Perl module to transform XML data:
<gml:boundedBy>
 <gml:Box>
     <gml:coordinates>89,43 90,43.5</gml:coordinates>
</gml:Box>
</gml:boundedBy>

I want to split the 89,42 90, 43.5 to two substrings as :
<gml:boundedBy>
 <gml:Envelope>
     <gml:lowerCorner>89,43</gml:lowerCorner>
     <gml:upperCorner>90,43.5</gml:upperCorner>
</gml:Envelope>
</gml:boundedBy>

I tried substring-after but didn't get results (XML::XSLT returned blank):
       <xsl:variable name="coords1" 
select="gml:boundedBy/gml:Box/gml:coordinates"/>
       <gml:lowerCorner>
          <xsl:value-of select="substring-before($coords1, ' ')"/>
       </gml:lowerCorner>
       <gml:upperCorner>
           <xsl:value-of select="substring-after($coords1,' ')"/>
       </gml:upperCorner>

Could anyone tell me why I cannot split the string: are there errors in my 
XSL; or, the module XML::XSLT does not support substring-after (it uses 
XPath1.3)? Anyone can recommend me another Perl module of XSLT processor?

Thank you very much!

n zhou