Copy elements from the topicref topicmeta to the corresponding topics' prolog

[gbebie-valerian-antidot]

Hi there,
My use case is the following:

• I transform @Audience attribute to an othermeta element and put it in a topicref of the corresponding topic, in a topicmeta.
• I achieve this transformation with the extension point : dita.xsl.mappull

However, I would also like to copy the newly created elements in the topicrefs to the prologs of the corresponding topics.
My difficulty is that I usually, when I apply transformation at the topic level and when I need info from the map, I use a param for the map such as <param name="input.map.url" expression="${html5.map.url}" if:set="html5.map.url"/> . but in this case, I need to apply the transformation with the topicpull extension point, and not in an html transformation. I need to apply the transformation in the source itself.

Would anyone has a simple example to share with me where the copy from the map to the topic could be applied?
Thanks for any pointer and tips!