Was already implicitly required (since 59387ddb) because RevBank::Amount
uses the "isa" feature, which was introduced in Perl 5.32 (but no longer
experimental since 5.36, not 5.32 as the old comment said).
Perl 5.32 was released in June 2020, and ships with Debian bullseye
("oldstable") which was released in August 2021.
Now implemented via a hidden user called '-cash'.
This also introduces the concept of hidden accounts, that begin with '+' or
'-', for result accounts and balance accounts. Future versions can further
use this for more detailed bookkeeping. The idea behind the sign is that
'-' accounts should be inverted to get the intuitive value. So if the account
'-cash' has -13.37, that means there should be +13.37 in the cash box (or,
well, once the rest of this is implemented and the initial values are then set
correctly.)
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.
