use MCE;

## Parse command line argument for $database_list

my $mce = MCE->new(
   max_workers => 4,
   chunk_size  => 1
);

$mce->foreach("$database_list", sub {
   my ($self, $chunk_ref, $chunk_id) = @_;

   my $database = $chunk_ref->[0];
   my @result = ();

   ## Query the database

   $self->sendto('file:/path/to/result.out', @result);
});