I'm not using a framework (probably my first mistake :-))

Sure:

sub new
{
  my $class     = shift;
  my $self      = fields::new($class);
  my %params    = @_;

  die "ID not defined\n" unless $params{ID};

  $$self{id}    = $params{ID};
  $$self{queue} = Thread::Queue->new();
  $$self{handler} = $handler_map{$params{HANDLER}};

  $$self{processThread} = threads->new(\&worker, \$self, %params);

  # Note: No need to explicitly bless the object, as it is already ble
+ssed.
  return $self;
}
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The $$self{processThread} = threads->new(\&worker, \$self, %params); line I am really not sure about. I need the worker thread to know which object it is part of (so it knows which Thread::Queue to watch), but it seems a bit clunky to me to effectively be passing in a reference to itself