Since Perl 5.36.7, core Perl commands do not support bare file-handles anymore by default. Backwards compatibility can only be restored via

use feature 'bareword_filehandles';

Bareword file-handles have an extremely good alternative in file handle objects (like CIO::File and CIO::Dir) since the beginning of this century, so it's time to ditch them for good in MailBox. Removed are

1. own internal use of bareword file-handles
2. own internal use of bareword directory handles (opendir)
3. remove support for library users passing GLOBs
4. meanwhile, check that a 3-arg open is used everywhere

Remove use and support for bareword filehandles (changes for 1, 3, and 4):

• patch Mail-Box-IMAP4
• patch Mail-Box-IMAP4 (2)
• patch Mail-Box
• patch Mail-Message
• patch Mail-Message (2)
• patch Mail-Transport

Remove the use of bareword directory handles (changes for 2)

• patch Mail-Box
• patch Mail-Box (2)