CREATE DATABASE Kalmuecke;
use Kalmuecke;
GRANT ALL PRIVILEGES ON Kalmuecke.* TO 'Kalmuecke'@'localhost' IDENTIFIED BY 'passwort';

CREATE TABLE kunden (
   kunde VARCHAR(255) NOT NULL,
   datensatz VARCHAR(255) NOT NULL,
   INDEX kunde_idx(kunde)
) TYPE=InnoDB;

INSERT INTO kunden values ('Meyer', 'DatensatzA 1');
INSERT INTO kunden values ('Meyer', 'DatensatzA 2');
INSERT INTO kunden values ('Meyer', 'DatensatzA 3');
INSERT INTO kunden values ('Meyer', 'DatensatzA 4');
INSERT INTO kunden values ('Meyer', 'DatensatzA 5');
INSERT INTO kunden values ('Meyer', 'DatensatzA 6');
INSERT INTO kunden values ('Müller', 'DatensatzB 1');
INSERT INTO kunden values ('Müller', 'DatensatzB 2');
INSERT INTO kunden values ('Müller', 'DatensatzB 3');
INSERT INTO kunden values ('Schulze', 'DatensatzC 1');
INSERT INTO kunden values ('Schulze', 'DatensatzC 2');
INSERT INTO kunden values ('Schulze', 'DatensatzC 3');
INSERT INTO kunden values ('Schulze', 'DatensatzC 4');
INSERT INTO kunden values ('Schulze', 'DatensatzC 5');
INSERT INTO kunden values ('Schulze', 'DatensatzC 6');
INSERT INTO kunden values ('Schulze', 'DatensatzC 7');

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
use DBI;

my %db = (
   name => 'Kalmuecke',
   user => 'Kalmuecke',
   pass => 'passwort',
   host => 'localhost',
   port => 3306,
   type => 'mysql',
);

my $kunde  = $ARGV[0] || die "Usage: $0 <kunde>\n";
my $select = "select datensatz from kunden where kunde = '$kunde'";

my $con = "DBI:$db{type}:database=$db{name};host=$db{host};port=$db{port}";
my $dbh = DBI->connect($con, $db{user}, $db{pass}) or die DBI->errstr;
my $sth = $dbh->prepare($select) or die $dbh->errstr;

$sth->execute() or die $sth->errstr;

my %kunden;

while (my $msg = $sth->fetchrow_hashref) {
   push @{$kunden{$kunde}}, $msg->{datensatz};
}

$sth->finish or die $sth->errstr;
$dbh->disconnect or die $dbh->errstr;

print Dumper(\%kunden);