Here is output using Dumper 
 
'abc,def' => {
               ',,,item4' => 1,
               'item1,,,' => 1,
               ',item2,,' => 1
              },
'kln,mno' => {
               ',,,item4' => 1
               'item1,,,' => 1
              },

[download]

And the result should look like 

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

[download]

In reply to Re^2: merge with multiple row with same key by tcheungcm
in thread merge with multiple row with same key by tcheungcm

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