Allow multiple variable replacments

Assume you have a date in a filename: test_20200204.mat

You want to use the contained date as a DATETIME in CaosDB. How would you do that?

Currently it is not possible to do sth. like this:

match: test_(?P<year>[0-9]{4,4})(?P<month>[0-9]{2,2})(?P<day>[0-9]{2,2})\.mat
records:
  Experiment:
    date: $year-$month-$date

Please implement some form of multiple variable replacements.