When asked to fix the bug, it came up with a different regex, which
would completely change what's valid and what's not, so that's totally
wrong:
/^\s*(-)?([0-9]+)(?:[,.]([0-9]{1,2}))?\s*$/
When asked to fix it in another way, without changing the regex, it
suggested stripping the sign completely, which is even more wrong.
So I fixed it myself :)
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.
