With this the user is now able to have a way about where the files are
going to be read and matched against the regular expression. It used not
to be necessary in the archive expansion mode, but is required now that
the feature is exposed in more cases.
When using LOAD CSV it's possible to load from filename matching a
regular expression, but for that to work the *csv-path-root* needs to be
properly setup at run-time.
