Koha
Koha, "the world's first free and open source library system", is a big Perl application used by lots of libraries around the world. It also has a big developer community, which hardly overlaps with the "Perl Conference Community".
Maybe this talk can help us to join forces.
I recently started to work on a project that uses Koha. While I've heard about this project, I (as most of the Perl people I know) have never actually looked into the project and it's big community. This has now changed (for me), and I have found a very helpful and smart group of people who work with old to ancient code (and even more ancient data formats..), but seem to manage the "Theseus ship" transformation very well.
Currently, Koha is a (to me still) weird mixture of old-school CGI scripts (run via mod_perl or Plack), a Mojolicous API, Template::Toolkit and a lot of tooling.
In this talk I want to show a few of the nice features of Koha, and some of it's "interesting" internals. And also MARC...
And maybe we can get a few more Perl experts to join Koha development?