use strict;
use Person;

my $person1 = Person->new;
$person1->name("goodname"); # pass a string literal
print "Good name: ", $person1->name(),"\n"; # the name is printed.


my $person2 = Person->new;
my $s = "badname";
if($s =~ /(.+)/){ #just to match anything
  $person2->name($1); # now pass $1, which is "badname"
}
print "Bad name:",$person2->name(),"\n"; # the name is lost!
__END__
Good name: goodname
Bad name:

##</code><code>##

package Person;
use strict;
use Carp;
use vars qw($AUTOLOAD %ok_field);

# Authorize four attribute fields
for my $attr ( qw(name age peers parent) ) { $ok_field{$attr}++; } 

sub AUTOLOAD {
    my $self = shift;
    my $attr = $AUTOLOAD;
    $attr =~ s/.*:://;
    return unless $attr =~ /[^A-Z]/;  # skip DESTROY and all-cap methods
    croak "invalid attribute method: ->$attr()" unless $ok_field{$attr};
    $self->{uc $attr} = shift if @_;
    return $self->{uc $attr};
}

sub new {
    my $proto  = shift;
    my $class  = ref($proto) || $proto;
    my $parent = ref($proto) && $proto;
    my $self = {};
    bless($self, $class);
    $self->parent($parent);
    return $self;
} 

1;