IO::Pty::HalfDuplex has some portability problems. There's also the typo read. There is no method read:-). Use recv instead. Neither Ptrace nor SysctlPoll worked, even though the module passed all tests. Here's what worked for me:

#!/usr/bin/perl

use strict;
use warnings;
use IO::Pty::HalfDuplex;

my $pty = IO::Pty::HalfDuplex->new;
$pty->spawn("nethack") or warn "Spawn failed: $!";

unless ( $pty->is_active ) {
    warn "$pty is not active";
}
else {
    print $pty->recv;
}
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