It's too buggy; in some edge cases it results in an infinite input loop
with 100% cpu. If you want to restart, use 'restart' instead of eof'ing
the input with ^D.
The signatures feature has been "experimental" since Perl 5.20 (May 2014), but
expected to stay. After 8 years I'm ready to take the risk :)
Have added Perl v5.28 (June 2018) as the minimum requirement, even though the
current revbank should work with 5.20, to see if this bothers any users. Perl
v5.28 is in Debian "buster", which is now oldstable.
