POE::Component::IRC::State and nick changes

Using POE::Component::IRC::State, I'm trying to access channels in which my
Perl program sees a user has changed his nick. This is the relevant
subroutine:

sub onnick{
my ($who,$newnick,$where) = @_[ARG0,ARG1,ARG2];
my ($nick, $host) = split /!/, $who;
my $channel = $where->[0];

my $logline = "--- " . $nick . " is now known as " . $target;

&writeline($ircserver, $channel, $logline);
}

Now, the documentation indicates that ARG2 will contain an arrayref of all
the channels on which the client saw the user change his nickname. Now,
for simplicity's sake, I'm just worried about the first one, which should
be in $where->[0].

However, it's not there.

Using Data::Dumper, I discover that ARG2 (and therefore $where) is an
arrayref, but it's empty.

Any clue what I'm missing? And yes, I am using
POE::Component::IRC::State->spawn rather than just
POE::Component::IRC->spawn.
--
Kurt M. Weber