$vHash{"101010"}{"S0"} = "sometext";

##</code><code>##

$vHash{"101010USED"}{"S0"}{"SYSTEM"} = "sometext";

##</code><code>##

${ $vHash{101010} }{S0} = 'sometext';

##</code><code>##

ref $vHash{101010}; # => 'HASH'
ref $vHash{101010}{S0}; # => undef
ref $vHash{101010USED}; # => 'HASH'
ref $vHash{101010USED}{S0}; # => 'HASH'