use DBI;
my $dbh;
my $dbConnectString = 'dbi:Oracle:ABCD'; # Connect to the ABCD database specified in tnsnames.ora
my $dbUser = 'myUsername';
my $dbPwd  = 'myPassword';

# Establish the Oracle database connections and initialize the database statement handle used later
unless ($dbh = DBI->connect($dbConnectString, $dbUser, $dbPwd, {RaiseError => 0, AutoCommit => 0 })) {
  die "Unable to connect to Oracle database ABCD as user $dbUser: $DBI::errstr: $!";
}
$dbh->{RaiseError} = 1; # So we don't have to check every DBI call we set RaiseError.

print "Connected\n";

$dbh->disconnect;
undef $dbh;