my $aktData = $aktivitaet->{'activityData'};
foreach my $data (@$aktData) {
   ...
}

##</code><code>##

my @aktData = @{ $aktivitaet->{'activityData'} };
foreach my $data (@aktData) {
   ...
}

##</code><code>##

use Data::Dumper;

my $data = {
  "list"    => ( "foo", "bar", "baz" ),
};

print Dumper($data);