If I just use once sysread to try, it is still empty. Here is the code, what is wrong in the code?

my $cmd = '/opt/rssh/bin/ssh';
my $machine = "remote_machine";

open(my $fh, "-|", "$cmd $machine \"hostname;sleep 5;uptime\" 2>&1") o
+r die "cannot open fh";

my $flags = fcntl($fh, F_GETFL, 0) or die "\ncan't get flags for the p
+ipe: $!\n";
fcntl($fh, F_SETFL, $flags | O_NONBLOCK) or die "\ncan't set flags: $!
+\n";

my $out = $fh;
my $bytes_read = -1;
my $blocksize = 1024;
my $result = "";
my $buf;

$bytes_read = sysread($out, $buf, $blocksize);

print "\nl buf content is:\n $buf \n";
close $out;
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