$tip will hold an IP address, but you're using it as an array index.

Here's how I might write the foreach loop:

foreach my $ip_port (@{$data{$ip}}) {    # $ip_port = ["192.168.0.3","
+43035"];

    $sock = IO::Socket::INET->new(Proto => 'udp',
                                  PeerAddr => $ip_port->[0],
                                  PeerPort => $ip_port->[1]
                                 );

    $sock->send($in) or die "send: $!";

    print "Sent to $ip_port->[0]:$ip_port->[1]\n";

}
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The trick here is that, once you have a reference to a sublevel of the data structure -- in this case $ip_port, which points to one of the inner arrays -- you can work directly from that reference.