Open filehandles
           Any filehandles open at the time of the fork() will be dup()-ed.
           Thus, the files can be closed independently in the parent and
           child, but beware that the dup()-ed handles will still share the
           same seek pointer. Changing the seek position in the parent will
           change it in the child and vice-versa. One can avoid this by
           opening files that need distinct seek pointers separately in the
           child.