my %hash = ( 
   'company' => 
        { 'microsoft' => 
              {'applications' => 
                      {'windows' => 'operating system', 'office' => 'office suite'}
                ,'people' => 
                      {'bill gates' => 'chair man'}
        }, 
         'sun microsystems' => 
               {'applications' =>
                      {'solaris' => 'operating system',
'star office' => 'office suite'}
        },
         'cross over' => 
               {}
    }
);

##</code><code>##

add_to_hash(\%hash,'scalar','companies-microsoft-people-steve ballmer','bills bulldog')
#and you suddenly decide to have another category
add_to_hash(\%hash,'list','companies-cross over-supports','iTunes','photo shop')
#or something more elegant