My two favourite Perl April Fools (taken from The Lighter Side of Perl Culture (Part VI): April Fools) are:
Black Perl (Larry Wall, 1990)
It has come to my attention that there is a crying need for a place for
people to express both their emotional and technical natures simultaneously.
Several people have sent me some items which don't fit into any newsgroup.
Perhaps it's because I recently posted to both comp.lang.perl and to
rec.arts.poems, but people seem to be writing poems in Perl, and they're
asking me where they should post them.
-- Larry Wall requests the formation of
a new comp.lang.perl.poems newsgroup
Parrot (Simon Cozens, 2001)
Today brought the official announcement that many of us in the Perl and Python
communities had been awaiting and expecting for some time now: the culmination
of the year-long collaboration between Larry Wall and Guido van Rossum, and
the establishment of a period of joint development between the developers of
Perl and Python.
-- Simon Cozens announces
Parrot, April 1, 2001
I was especially tickled by this Parrot code sample:
# copy stdin to stdout, except for lines starting with #
if dollar_underscore =eq= "#":
Perl April Fools Timeline