Your best bet is to fork your in own program and let the parent keep track of the childs PID. Make your system() call in the child. When you are ready to terminate it, call kill on the childs PID.

I would write some code for you, but there is tons out there:

Link to Perl Cookbook ch 17 section 13 removed Forking
Link to Perl Cookbook, ch 16 section 01 removed. Process Management
Link to Perl Cookbook chapter 16 section 03 removed Exactly what you want

And so on (you might notice that these are all from the Perl Cookbook). Good luck.

Links to copyrighted material posted without express permission of author and publisher removed to eliminate copyright violation by davido per consideration.