my $user = 'test';
my $pass = 'passwd';
my $host = 'localhost';
my $db = 'datenbankname';
my $driver = "dbi:mysql:$db:$host";
my $dbh = DBI->connect($driver,$user,$pass) or die $DBI::errstr;
my $string = 'Thueringen';
$string =~ s/ue/ü/g;
my $string = $dbh->quote($string);
my $test = $dbh->prepare("SELECT * FROM table WHERE zeile=$string;");
....
$dbh->disconnect();