write(1, "torm-control broadcast level 10."..., 4096) = 4096
write(1, "rol broadcast level 10.00\n1782: "..., 4096) = -1 EAGAIN (Re
+source temporarily unavailable)

[download]

The only plausible explanation I can think of is OpenSSH ssh setting STDOUT into non-blocking mode. BTW, how are you capturing STDOUT?

Add a dump of /proc/$$/fdinfo: 

open OUT, ">", "./trace.out";

for (0, 1, 2) {
    local $/;
    open my $fdinfo, '<', "/proc/$$/fdinfo/$_";
    my $info = <$fdinfo>;
    print OUT "fdinfo $_:\n$info\n\n";
}

my $line =0;
foreach (@cmdout) {
    $line++;
    my $bytes = print  $line.": ".$_;
    print OUT "$line: bytes: $bytes, err: $! \n";
}
close(OUT);

[download]

The non-blocking flag is 0x4000. You may also like to generate dumps of fdinfo before the constructor call and before and after calling capture.

In reply to Re^19: Net::OpenSSH loosing lines ins reply by salva
in thread Net::OpenSSH loosing lines ins reply by Andy16

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