Does a fork(2) system call. Returns the child pid to the parent process and 0 to the child process, or undef if the fork is unsuccessful. Note: unflushed buffers remain unflushed in both processes, which means you may need to set $| ($AUTOFLUSH in English) or call the autoflush() FileHandle method to avoid duplicate output.
If you fork() without ever waiting on your children, you will accumulate zombies:
There's also the double-fork trick (error checking on fork() returns omitted);