2012.12.01 in #71Advent Calendars Calendar
Len Jaffe created an Advent Calendar pulling together the links to the Advent postings on the various other calendars. Mostly Perl though there are some others as well.
2014.12.01 in #175Advent Planet 2014
Len Jaffe maintains and Advent calendar collecting the links to other advent calendars.
2016.12.01 in #280Advent Planet
As every year Len put together the list of all the Advent calendars.
2016.12.01 in #281Advent Planet
The Avent Plannet where you can find links to the articles of all the articles published in the Advent calendars. 8 of those seem to be Perl-related.