Not between process instances, but between multiple instances of the same class in one process. And I figured it out. It was as simple as:

sub init {
  ## initialize stuff
  $cache=new GNS::Cache;
}
sub uninit {
  undef $cache;
}
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then from the main program, I can just do a

GNS::Node::init();
my $x=new GNS::Node;
my $y=new GNS::Node;
## blah blah blah
## do some stuff
GNS::Node::uninit();
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