From the documentation of recv:

Returns the address of the sender if SOCKET's protocol supports this; returns an empty string otherwise. If there's an error, returns the undefined value.

This means the while loop will terminate when the call happens to return a false value. This works for me:

while (1) {
    defined $sock->recv($data, 1024)
        or die "recv error: $!";
    ...
[download]

Update 2019-08-17: Updated the link to "Truth and Falsehood".