So if this was the answer I would have to say thats a design fault

I get the same. For a simplistic workaround, instead of

$chan->write("$intext\n");
$chan->send_eof();
[download]

do

while (length $intext > 32767) {
  $chan->write(substr($intext, 0, 32768, ''));
}
$chan->write("$intext\n");
$chan->send_eof();
[download]

Doing that, I then get:

ssh created
ssh connected
cmd is wc
intext length is 100000
      1       1  100001
remote exit status is 0 bytes returned is 24 bytes
[download]

Cheers,
Rob