Specifically, the fork Posix system call makes an exact copy of the parent process, including all memory segments. Both the parent and the child resume execution exactly as if they had each made the fork system call. Usually, program switches execution paths based on the return value of the fork call in order to learn whether it is the child or the parent.

You are running Windows, which doesn't have the fork system call, so you are using Perl's emulation of it within the Perl interpreter. To learn more about the limits of this emulation, run perldoc perlfork or read the perldoc page here.