class grafik-batang {
  has Int @.nilai-batang;
  method plot {
    say @.nilai-batang;
  }
}

class grafik-garis {
  has Int @.nilai-garis;
  method plot {
    say @.nilai-garis;
  }
}

class grafik-gabungan is grafik-batang is grafik-garis {
  method plot {
    say @.nilai-batang;
    say @.nilai-garis;
  }
}

my $penjualan-aktual    = grafik-batang.new(nilai-batang => [10,9,11,8,7,10]);
my $perkiraan-penjualan = grafik-garis.new(nilai-garis => [9,8,10,7,6,9]);

my $aktual-vs-perkiraan = grafik-gabungan.new(
                                        nilai-batang => [10,9,11,8,7,10],
                                         nilai-garis => [9,8,10,7,6,9],
                                     );
say "Penjualan aktual:";
$penjualan-aktual.plot;
say "Perkiraan penjualan:";
$perkiraan-penjualan.plot;
say "Aktual vs Perkiraan:";
$aktual-vs-perkiraan.plot;