package MyDatabase::DBI;
use base qw(Class::DBI::mysql);
my %config;
use Config::General;
my $conf = new Config::General(
  -ConfigFile => '/usr/local/configfiles/library.site.conf',
  -InterPolateVars => 1
                              );
%config = $conf->getall;

my $dsn = "DBI:mysql:host=$config{DB_HOST};database=$config{DB_NAME}";
my $db_user = $config{DB_USER};
my $db_pass = $config{DB_PASS};

__PACKAGE__->set_db('Main', $dsn, $db_user, $db_pass);
# etc.