my @newdeck= shuffle(@starting_deck);

sub shuffle {
  my @cards= @_;
  foreach (1...30) {
    my @cut= pop(@cards), shift (@cards), pop(@cards) ...
    ...
    push @cards, @cut;
  }
  ...
  return @˘ards;
}

##</code><code>##

use Data::Dumper; # <-better put this at the beginning of your script, but works here too

print Dumper(\@starting_deck);