regex grouping precedence.

http://www.w3.org/TR/xslt20/#element-matching-substring seems to say
little about how nested grouping is numbered.

(...) (....) ( ....)
gives regex-group (1,2,3) OK.

(...) (....)| ( ....)
  Is the third group counted as two due to the alternates?
or still 3?

(...) ( (..)(.).) ( ....)
1     2 3   4     5
is how I would expect to number them,
but I'm totally unsure.

Using xslt 2 to parse a plain text file;

Input string
500748,500748              ,Set My People Free  

regex

 <xsl:for-each select='tokenize($f, "[\r]?\n")'>
    <r> 
  
         <xsl:analyze-string  flags="ix"
         regex="([0-9]{{6}})
         (,,)|(,([0-9]{{6}})\p{{Zs}}+,(.*))$" 
          select=".">
    <xsl:matching-substring>
      <bibno><xsl:value-of select="regex-group(1)"/></bibno>
      <ck><xsl:value-of select="normalize-space(regex-group(4))"/></ck>
      <ttl><xsl:value-of select="normalize-space(regex-group(5))"/></ttl>
    </xsl:matching-substring>
    <xsl:non-matching-substring>
          <n><xsl:value-of select="."/></n>
    </xsl:non-matching-substring>
  </xsl:analyze-string>
    
   
</r>
</xsl:for-each>
   

output is 

      <n>500748</n>
      <bibno/>
      <ck>500748</ck>
      <ttl>Set My People Free</ttl>


Regards DaveP.

**** snip here *****

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