my ($accessToken, $appId, $userId) = (shift, shift, shift);
  use threads;
  use Thread::Queue;
  use WWW::Curl::Easy;
  use WWW::Curl::Form;

  my $threadLimit = 1;
  my $testUsers=listTestUsersFull($accessToken, $appId);
  my $q = Thread::Queue->new();    # A new empty queue
  # Worker threads
  my @thr = map {
    threads->create(sub {
      while (my @item = $q->dequeue(2)) {
        # assuming undef isn't a valid value and so can be a marker.
        last unless defined $item[0];
        last unless defined $item[1];
        deleteUser($item[1], $appId, $item[0]);
      }
    } , $appId
   )->detach();
  } 1..$threadLimit;

# Send work to the threads
@testUsers = @testUsers[1..5];
  foreach (keys %{$testUsers}){
    $q->enqueue($userId, $$testUsers{$userId}->{access_token});
  }

# send markers.
  $q->enqueue(undef) for (1..$threadLimit);

# terminate.
  $_->join() for @thr;