I tried your script, and it needed

use Gtk2 qw (init');
use IO::Socket;
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to get it to run. Then,

  my $conn = IO::Socket::INET->new(PeerAddr => $host, PeerPort => $por
+t, Proto => 'tcp') or popup_err(1);
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caused the error to popup. Remove the popup_err(1) and it seems to start.

I didn't try to debug it any further, because the tie %ready looked kind of complex to me.