$Menu_Multi_Hash{'L1A'}{'L2A'} = 'none';

etc.. etc.. and for the last one, it will be

$Menu_Multi_Hash{'L1A'}{'L2A'}{'L3B'}{'L4A'} = 'exe command';

(please note that the first three elements are the ones arrived by splitting the 'Title', the fourth is the 'Text' and the right hand side is the 'Action')