perl - need a help on working with excel file

I have a excel having 2 columns of values as below:
col A col b
39383 908
39384 908
39384 983
39385 966
39386 908
39386 983
39387 992

Hi. I am new to this perl and i have one small requirement. I want the result of those values as below:
Col A col B
39383 908
39384 908,983
39385 966
39386 908,983

Col A values has mapping one to many. Eg:
39384 has repeated in col A which is pointint 2 values 908 and 903. I need to unique id's in col A and col B should has all of its values seperated by comma. can anybody help me to do this taskk