package MyClass;
sub new {
    my ($class, %args) = @_;
    return bless \%args => $class;
}
sub add {
    my ($self, %args) = @_;
    while (my ($k, $v) = each %args) {
        $self->{$k} = $v;
    }
    return $self;
}
sub greet {}

package main;
my $obj = MyClass->new(message => "Guten Morgen", nachname => "Wall", vorname => "Larry");
$obj->add(bla => 'blubb', foo => 'bar');
use DDP; p $obj;
__END__
MyClass  {
    public methods (3) : add, greet, new
    private methods (0)
    internals: {
        bla        "blubb",
        foo        "bar",
        message    "Guten Morgen",
        nachname   "Wall",
        vorname    "Larry"
    }
}

sub new{
    my $class = shift;
    my %att = (
        name  => 'Foo',
        vname => 'Bär',
    @_);
    bless{
        name => $att{name},
        vname => $att{vname},
        USER => {}
    }, $class;
}

sub add{
    my $self = shift;
    my $att = shift;
    my $val = shift;
    $self->{USER}{$att} = $val;
}

my $m = main->new(name => 'booooo');
$m->add('PLZ','12345');
puts Dumper $m;

# das gibt aus:
$VAR1 = bless( {
                 'USER' => {
                             'PLZ' => '12345'
                           },
                 'name' => 'booooo',
                 'vname' => 'Bär'
               }, 'main' );