use DBI;

my $DB_NAME = "test";
my $DB_USER = "xxxx";
my $DB_PASS = "xxx";

$test_data = DBI->connect("DBI:mysql:$DB_NAME","$DB_USER","$DB_PASS");

$data= checkdb($var1,$var2,$var3); ##  die Variablen var1-var3 werden in einer Schleife produziert, habe ich hier mal alles weggelassen





sub checkdb{

my $chr_id = $_[0];
my $left =  $_[1];
my $right = $_[2];

    my $query = "SELECT loc, mark, val FROM test WHERE chr_id = $chr_id AND loc BETWEEN $left AND $right";
    my $query_handle = $test_data->prepare($query);
    $query_handle->execute();

    my $data;
    while(my($loc, $mark, $val) = $query_handle->fetchrow_array()) {
	$data->{$mark}->{$loc} = $val;
    }

    return $data;
}
}