package Student;
sub new { # Constructor
	my $class = shift;
	my $data={};
	our $students;

	my $ref = sub { # Closure
		my ($access_type, $key, $value) = @_;

		if ($access_type eq "set") {
        		$data->{$key} = $value;  
                        # $data still available here
		}
		elsif ($access_type eq "get") {
			return $data->{$key};
		}
		elsif ($access_type eq "keys") {
			return (keys %{$data});
		}
		elsif ($access_type eq "destroy") {
			$students--;
			return $students;
		}
		else {
		 die "Access type should be set or get";
		}
                print "New student created, we have ", 
                  ++$students, " students.\n";
		bless ($ref, $class);  
                  # bless anonymous subroutine
	}
} # End constructor

sub set {
	my ($self, $key, $value) = @_;  
            # $self reference anonymous sub
	$self->("set", $key, $value);
}

sub get {
	my ($self, $key) = @_;
	return $self->("get", $key);
}

sub display {
	my $self = shift;
	my @keys = $self->("keys");
	@keys=reverse(@keys);
	foreach my $key (@keys) {
	  my $value = $self->("get", $key);
	  printf "%-25s%-5s:%-20s\n", $self, $key, $value;
	}
	print "\n";
}

sub DESTROY {
  my $self = shift;
  print "Object going out of scope:\n";
  print "Students remain: ", $self->("destroy"), "\n";
}

1;