[xsl] Need an XPath expression which checks that all commas are escaped

["Costello, Roger L. costello@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

Hi Folks,

I need an XPath 2.0 expression for this:

	Check that each comma in the <value>
 	element is escaped with a backslash.

Examples:

This is good:

<value>A\, B</value>

This is bad:

<value>A, B</value>

This is also bad, because one comma is escaped but the other is not:

<value>A\, B, C</value>

I created an XPath expression to see if the text is good:

tokenize(text(), ',')[position() lt last()][ends-with(., '\')]

I think that is correct. Is there a simpler XPath expression to solve this?

/Roger