In the end I found that a "reasonable" tradeoff in term of portability is
the following solution based on "select" and "repeat".

use IO::Select;
my ($server, $server_port, $timeout, $maxlisten);
$maxlisten=5;
$timeout=50;
if (@ARGV<1) { 
    $server_port=9876;
} else {
    $server_port=shift;
}
my $top = MainWindow->new();

$server = IO::Socket::INET->new(LocalPort => $server_port,
                                 Type      => SOCK_STREAM,
                                 Reuse     => 1,
                                 Listen    => $maxlisten );
$top->repeat($timeout,[\&recedata, $server]);

MainLoop();

sub recedata {
        my $server=shift;
        my $s=IO::Select->new($server);

        my @ready=$s->can_read(0);

        if ($ready[0] == $server) {
            warn "in recedata\n";
            my $client=$server->accept();
            my $data=<$client>;
            print "$data\n";
            my $t2 = $top->Scrolled('Text');
            $t2->pack(-expand => 1, -fill => 'both');   
            tie (*TEXT2, 'Tk::Text',$t2);
            print TEXT2 "$data\n";
            close ($client);
        }
}
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Thanks to all people who replied to my question!