Apache Pig - Not able to read the bag

I am trying to read the comma separated data using PIG as below:

grunt> cat script/pig/emp_tuple1.txt
1,kirti,250000,{(100),(200)}
2,kk,240000,{(100),(300)}
3,kumar,200000,{(200),(400)}
4,shinde,290000,{(200),(500),(300),(100)}
5,shinde k y,260000,{(100),(300),(200)}
6,amol,255000,{(300)}
grunt> emp_t1 = load 'script/pig/emp_tuple1.txt' using PigStorage(',') as (empno:int, ename:chararray, salary:int, dlist:bag{});
grunt> dump emp_t1;
2015-11-23 12:26:44,450 [main] INFO  org.apache.pig.backend.hadoop.executionengine.util.MapRedUtil - Total input paths to process : 1
(1,kirti,250000,)   
(2,kk,240000,)
(3,kumar,200000,)
(4,shinde,290000,)
(5,shinde k y,260000,)
(6,amol,255000,{(300)})

In between it is showing a warning as:

2015-11-23 12:26:44,173 [LocalJobRunner Map Task Executor #0] WARN  org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigHadoopLogger - org.apache.pig.builtin.Utf8StorageConverter(FIELD_DISCARDED_TYPE_CONVERSION_FAILED): Unable to interpret value [123, 40, 49, 48, 48, 41] in field being converted to type bag, caught ParseException <Unexpect end of bag> field discarded

It seems it is showing the warning when it encounters the comma (,) in the bag.

Now what I did is: change the comma to tab (or any other separator) and it worked:

grunt> cat script/pig/emp_tuple2.txt;
1|kirti|250000|{(100),(200)}
2|kk|240000|{(100),(300)}
3|kumar|200000|{(200),(400)}
4|shinde|290000|{(200),(500),(300),(100)}
5|shinde k y|260000|{(100),(300),(200)}
6|amol|255000|{(300)}
grunt> emp_t2 = load 'script/pig/emp_tuple2.txt' using PigStorage('|') as (empno:int, ename:chararray, salary:int, dlist:bag{});
grunt> dump emp_t1;
2015-11-23 12:31:33,408 [main] INFO  org.apache.pig.backend.hadoop.executionengine.util.MapRedUtil - Total input paths to process : 1
(1,kirti,250000,{(100),(200)})
(2,kk,240000,{(100),(300)})
(3,kumar,200000,{(200),(400)})
(4,shinde,290000,{(200),(500),(300),(100)})
(5,shinde k y,260000,{(100),(300),(200)})
(6,amol,255000,{(300)})

So I am just wondering if you have comma sepqrated data with bags separated with comma, will it not work?

Lets go into details, 
 1. Data is being read as TextInputFormat 
 2. Line Record Reader is being used to read lines
 3. , is being used to separate columns. 

as "," occurs in the bag and is the delimeter across columns, bag is being split into multiple columns. 

There are various way to overcome this. 

 1. pre-process the input and replace first three "," in each row by some other delimeter.