Hi,
I've got a quick look in the Cookbook.
There is a Module IPC::Shareable, which allows you
to share a variable between many processes. Maybe this help's.
Or another idea is that your childprocesses do not send a SIGNAL after
every mail send, but after 10,20,30. So your Parent process got not that much Signals. But normaly I would say,
that the SIGUSR2 - Methode should work.

A third way might be to open your childs with pipe.
like:

use IO::Handle;
if ($pid = open(CHILD1, "-|")) {

  here you can read fom STDIN that what your child will tell you,
  but I don't know if this methode works with multiple childs.
}
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