The query string-queries-results-q5 does this:

    <item_summary>
        { concat($item/title,". ") }
        { concat($item/date,". ") }
        { string(($item//par)[1]) }
    </item_summary> 

that is, three expressions in curly braces. In the supplied test results, a
single space has been inserted between the results of the first and second of
these expressions, and also between the second and third. So the inserted
full-stops are followed by two spaces rather than one as requested.