'abc,def' => {
               ',,,item4' => 1,
               'item1,,,' => 1,
               ',item2,,' => 1
              },
'kln,mno' => {
               ',,,item4' => 1
               'item1,,,' => 1
              },

##</code><code>##

'abc,def' => { 'item1,item2,,item4 },
'kln.mno' => { 'item1,,,item4 },