Add non-zero exit status to the usage sub
Set version requirement to minimum
Add a note to README
Add a check for relative paths
Clarify README

There was written something about the 'modification' of files. Make that
refer to the ctime.

Why the ctime? On my computer I have got a directory named 5 for files
that shall be deleted after five days of non-modification. However, if I
have a file lying around somewhere else and decide that it should be
deleted in five days and therefore put it in 5, it may well be that
mtime says the file hasn't been modified for 5 days and it is deleted
immediately.

It probably should be an option to the user which time to use. But not
now.
Add the flesh of the deletion sub
Change time thing back to mtime

The early commit message about ctime is still somewhat valid. However,
testing the ctime version of Moirai is rather hard and the drawbacks of
mtime are not so severe. Thus use mtime for determining the date of
expiry.
Start writing tests

I started writing test, but I think that a little overkill for now.  For
packaging, tests have to be written, of course.