The pseudo-code for the way I imagine implementing this is something like:

use DataBaseDriver;
...
use constant CITIES       => qw(lon par);
use constant APPLICATIONS => qw(test prod);

# build dispatch table for database handles
my %db_handle;
for my $city (CITIES) {
    for my $app (APPLICATIONS) {
        $db_handle{$city}{$app} = DataBaseDriver->new
            or die "'$city:$app' driver creation failed: ",
                   DataBaseDriver->error_msg;
        }
    }
...
# use database handle dispatch table
my $msg  = '...';
my $city = '...';
my $app  = '...';

my $dbh = $db_handle{$city}{$app}
   or die "'$city:$app' driver access failed";

$dbh->store_to_database($msg);
...
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