$vHash{"101010"}{"S0"} = "text";
$vHash{"101010USED"}{"S0"} = "text";
if (!exists($vHash{"101010"}{"S0"}{"SYSTEM"})) {
    $vHash{"101010"}{"S0"}{"SYSTEM"} = "TEXT";
    print "First<br>";
}
if (!exists($vHash{"101010USED"}{"S0"}{"SYSTEM"})) {
    $vHash{"101010USED"}{"S0"}{"SYSTEM"} = "TEXT";
    print "Second<br>";
}