Help about xpath expression

[Sam Sahara]

In some search operations in calibre one can use an xpath expression to get the values for particular tags, i.e. the following expression:

//h:div[re:test(@class, "figbox", "i")]

selects the content of a "div" tag whose "class" attribute is set to "figbox", so in the following html line:

<div class="figbox">Volterra</div>

the preceding xpath expression get the value "Volterra".

Now, with the following processing-instructions

<?bag value="2" content="Volterra"?>
<?bag value="3" content="Ferrara"?>

which xpath expression can I use to obtain the value "Ferrara" and not "Volterra"?

EDIT ===============================

I've tried putting in a book the following line

<?bag value="3" content="Ferrara"?>

and trying the following expression to add the word "Ferrara" in the ToC:

//processing-instruction("bag")[@value="3"]/@content

but I get only

"calibre, version 3.30.0
ERROR: No items found: No items were found that could be added to the Table of Contents.

ss

[Sam Sahara]

Originally Posted by Sam Sahara

EDIT ===============================

I've tried putting in a book the following line

<?bag value="3" content="Ferrara"?>

and trying the following expression to add the word "Ferrara" in the ToC:

//processing-instruction("bag")[@value="3"]/@content

but I get only

"calibre, version 3.30.0
ERROR: No items found: No items were found that could be added to the Table of Contents.

Same result with the following expression:

substring-before(substring-after(//processing-instruction('bag'), 'value="3" content="'), '"')