I am working on a postback script that is having some weird problems trying to kill a firefox instance that is being loaded. Essentially what I need is to be able to have a non-blocking child thread running firefox that I can kill from it's parent thread to restart it, that I can push tabs to from a loop. But I can't get firefox to stop ghosting when I spawn it. Here is a short example of what I am trying to do:

#!/usr/bin/perl

# Test
my $pid = run_in_bg();
sleep 5;
system("firefox","-remote","openURL(http://www.google.com,new-tab)");
sleep 2;
kill 9, $pid;
sleep 5;
system("ps auxf");

sub run_in_bg
{
    $pid = fork();
    if($pid==0) {
        exec("firefox -private about:blank");
        exit(0);
    }   
    return $pid
}
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Anyone see what I am doing wrong?