sub large_array {
  my @large_array;
  ...populate @large_array...
  return @large_array;
}

sub large_array_ref {
  my $large_array_ref = [];
  ...populate @$large_array_ref...
  return $large_array_ref;
}

# Is the returned array copied?

@c = large_array();
@c = @{ large_array_ref() };