Not to add to your choices, but whenever I am faced with this I use Hash::Util's lock_keys method as follows....

package Dog;
use Hash::Util qw(lock_keys);
use Data::Dumper;

sub new
  {
    my $pkg = shift;
    my $ref = {};
    bless $ref, $pkg;
    lock_keys(%$ref,qw(intelligence));
    $ref->{intelligence} = shift;
    $ref;
  }

sub is_stupid {
    my $self = shift;
    return $self->{inteligence} < 3;
}


my $lassie = Dog->new(10);
print Dumper($lassie);
print "Lassie is ", $lassie->is_stupid ? "dumb" : "smart";
[download]

In the case of subclassing this, it should be easy enough to call unlock_keys, do what you need, and then lock it again.

This novice wasn't aware of the other methods you mention for achieving this, and would be interested in hearing what other monks might say of the methods described here.

Of course this only gives one runtime checks, but those are sufficient for my purposes.

---

---

• Are you posting in the right place? Check out Where do I post X? to know for sure.
• Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:

  <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>

• Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
• Want more info? How to link or How to display code and escape characters are good places to start.