sysread does not guaranteed, that all 5 bytes can be readed in one block. so you should add a loop over the sysread command. 
my $pos = 0;
while ( $pos < 5) {
    my $c = sysread $sock, $pong, 5, $pos or die $!;
    $pos += $c;
}

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In reply to Re^2: AJP ping by Anonymous Monk
in thread AJP ping by jffry

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