#! perl -lw
use strict;
use threads;
use IO::Socket;

my $lsn = new IO::Socket::INET(
    Listen => 5, LocalPort => '12345'
) or die "Failed to open listening port: $!\n";

async{
    print 'accept starting';
    my $c = $lsn->accept;
    print 'accept returned';
}->detach;

sleep 2;

print "-d starting";
-d $lsn;    # Freezes
print "-d returned";