You and Tye reminds me of the right solution to my problem.It seems that the FileHandle was not updated in child process. I therefore created a FileHandle in each child process instead of the parent process. Anyway, it is my own understanding. If someone know it, do drop me your message.

In reply to Re^5: missing values when using Parallel::ForkManager by Anonymous Monk
in thread missing values when using Parallel::ForkManager by plagent

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