Code modernization

Actions taken within the NLnet supported MailBox mid-life upgrade, work-package code modernization. Most MailBox code was written between 1999 and 2005, with perl 5.8 (first stable unicode) as backwards compatibility base. Many improvements have been made to Perl since, and some syntax got deprecated.

The new minimum Perl version to run MailBox is 5.16:

• use no newer syntax than 5.16 (released 2012)
• do not use syntax which is deprecated in 5.42 (released 2025)

The following changes have/are being made:

• Generic code practice clean-up (ongoing effort)
• Update minimal Perl version in all modules (completed)
• Remove support for bare file-handles (completed)
• use of s///r (completed)
• use of //, the defined-or (completed)
• optimize regular expressions
• use IO::Layers