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.
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 :)
