Yet Another Perl Conference.

Gathering(s) focused on the programming Language of All Love and All Joy that is Perl.

To plagiarize the web site:

The Yet Another Perl Conferences (YAPCs) are grassroots symposia on the Perl programming language under the auspices of the Yet Another Society (YAS), a non-profit, 501(3)(c) corporation for the advancement of collaborative efforts in computer and information sciences.

The silly acronym comes from Perl's (and indeed Hacker Cultures) long history of them, such as the well-known "JAPH".