my @array_child = qw(1 2 3 4);
my @array_parent = qw(5 6 7 8);

my ($child_ref,$parent_ref) = methode(\@array_child,\@array_parent);

sub methode{
  my ($ref_child,$ref_parent) = @_;
  my @child = @$ref_child;
  my @parent  = @$parent;
  # mach was
  return \@child,\@parent;
}