May I make another suggestion? This is originally from the Perl 4 Camel, but it actually works very well to prevent zombies:

 unless (fork) { # this is the child
    unless (fork) { # this is the grandchild
       exec "yourprogram";  # the detached process
                            # can also be perl code and exit(0)
    }   # exits when done
    # Back in the child
    exit 0;  # immediately terminates
 }
 wait; # gets rid of the terminated child immediately

This works because the child process exits immediately and is wait()ed on immediately, so no zombie. The grandchild ends up as a child of init because its parent has exited, and init will take care of reaping the grandchild for you.