killing all child processes created in a test

[Jonathan Swartz]

I have a series of test scripts that launches server subprocesses of  
different kinds - httpd, HTTP::Server::Simple, etc. A test script  
might launch multiple instances of each type of server. I'd like to  
behave well and kill all these children before the test exits. But  
it's a pain to keep track of all the child pids, especially when the  
code that creates the subprocess is many levels down from the test  
script itself.

Is there any way to automatically kill all the child processes created  
by a script (and their descendents)? For example, can I catch each  
subprocess creation somehow and record the pid in a global array?

At first I tried using Proc::ProcessTable to find all the processes  
where ppid = $$:

   sub kill_my_children {
       my $self = shift;

       my $t              = new Proc::ProcessTable;
       my $get_child_pids = sub {
           map { $_->pid } grep { $_->ppid == $$ } @{ $t->table };
       };
       my $send_signal = sub {
           my ( $signal, $pids ) = @_;
           explain( "sending signal $signal to " . join( ", ", @ 
$pids ) . "\n" );
           kill $signal, @$pids;
       };

       if ( my @child_pids = $get_child_pids->() ) {
           $send_signal->( 15, \...@child_pids );
           for ( my $i = 0 ; $i < 3 && $get_child_pids->() ; $i++ ) {
               sleep(1);
           }
           if ( @child_pids = $get_child_pids->() ) {
               $send_signal->( 9, \...@child_pids );
           }
       }
   }

But that doesn't work, because some servers, like httpd, launch in  
such a way that the parent httpd process ends up with ppid = 1.

Thanks
Jon