Perl

ERP
https://github.com/ledgersmb/LedgerSMB if Perl is dying language, then why was LedgerSMB written, a double-entry accounting system, featuring quotation, ordering, invoicing, projects, timecards, inventory management, shipping and more? see https://github.com/ishanvyas22/awesome-open-source-systems

perl on oop
Perl perspective (perl iteration)

vids
https://www.youtube.com/watch?v=jVTjaFVUenc

links
Perlmonks oop