Code:
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$ cat f29
MessageFlow,1,BusIntBatchMgr,a
OOBEvent,1,BusIntBatchMgr,a
TaskEvents,1,,a
MTTrace,1,,a
MTWarning,,1,a
MessageFlow,1,Batch,a
OOBEvent,1,Batch,a
TaskEvents,1,,a
EAISAPIdocWizard,1,BusIntMgr,a
EAISAPBAPIWizard,1,BusIntMgr,a
EAISiebelWizard,1,BusIntMgr,a
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$ perl -F, -plane '$F[2] eq "" ?{$F[2]=$x}:{$x=$F[2]}; $_=join(",",@F)' f29
MessageFlow,1,BusIntBatchMgr,a
OOBEvent,1,BusIntBatchMgr,a
TaskEvents,1,BusIntBatchMgr,a
MTTrace,1,BusIntBatchMgr,a
MTWarning,,1,a
MessageFlow,1,Batch,a
OOBEvent,1,Batch,a
TaskEvents,1,Batch,a
EAISAPIdocWizard,1,BusIntMgr,a
EAISAPBAPIWizard,1,BusIntMgr,a
EAISiebelWizard,1,BusIntMgr,a
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