That one does it perfectly. Thanks.

By replacing the $p in the map:merge(($p b& with ., the two maps are merged.
Is that how this works?

Maps are black boxes to me. Is there a way to bseeb inside? With a
variable, you can do a copy-of to see if everything is okay in there. When I
try to copy a map I get an error.

Thanks again for all the help.
>
>      <xsl:apply-templates
>        select="for $p in p[@class = 'nl']
>                return $groups
>                       !
>                       map:merge(
>                         (.,
>                          map { 'p' : $p })
>                       )"/>