So far, Nyom
Moritz , all works fine to progress step by step. No real problems seen in regard of index as it is used only for the selection of avaliable files while the search is done direct in the files (so no need of refreshing / new indexing, except new files are added).
Page lookup
BatchEdit uses DokuWiki page index to get the list of existing pages instead of going through the data directories. If the index is incomplete the plugin will not see some pages. This also applies to the “special” pages, for example, namespace templates.
So it's only about the list of files that batchEdit uses the index.
Index it self: Not sure for now, but it seems so, that refresh index matches also new files. It works not too slow.
In regard of regex, yes, the returns seems to be special. Hier $ seems to work more, as for place a string \1 = $1, maybe it works also for \L = $L (did not try for now).
Since Atma does not intent to learn/invest much in this skills, when ever a need arises, he would look and maybe addopt, investigate samples given here around.
It's good then, steo by Step, to make explainary pages on ATI.eu in all regards, for further future easier work and transfer.
http://accesstoinsight.eu/doku.php?id=de:tech:regex_use z.b.