Well, exec replaces a single process with
another, but fork copies the running process.
So, fork combined with exec is
the way (at least under Unix) to spawn off new
tasks. If you are doing a system, behind the
screens, Perl will do a fork and an exec.
It will just wait for the child to finish before continuing.
Using a system with an ampersand tacked to the
end of the command is an option, but that means Perl will
first invoke a shell (using fork and exec)
which will spawn off your command (using another fork
in reply to spawning multiple child processes