This is probably not The Right Way, but I had the thought the other day that one way to deal with this sort of problem is to run the child processes under fictitious names that include a label to identify the parent. So, for example, you might run httpd as "httpd_by_$$", then you could grep through the process list for "by_$$" to find pids you want to zap.

Note: if you're using the list form of exec or system, the first entry in the list is the name that appears in the process listing, as opposed to the actual name of the program you're launching. Here's a somewhat hacky proof-of-concept (single child case):

my $progname = 'emacs';
my $label = "_by_" . $$;
my $proglabel = $progname . $label;

my @args = ( $0 );

if ( my $pid = fork ) { 
  # this is parent code
  # pause, then zap the child
  sleep 10;
  my @lines = grep{ m/$label/ } qx{ ps axw };
  my @pids = map{ ( split " ", $_ )[0] } @lines;
  foreach my $pid ( @pids ) {
    my $status =
      kill 1, $pid;
    ($DEBUG) && print STDERR "Tried to kill (1) pid $pid, status: $sta
+tus \n";
  }
} else { 
   # this is child code
  die "cannot fork: $!" unless defined $pid;
  exec { $progname } ( $proglabel, @args );
}
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