package magic;

sub TIESCALAR {
    my $class = shift;
    die "Incorrect number of parameters" if @_ % 2;
    my $self = bless {}, $class;
    $self->_Init(@_);
    return $self;
}

sub _Init {
    my ($self, %opt) = @_;
    $self->{PRE}  = $opt{PRE}  || sub { return uc $_[0] };
    $self->{POST} = $opt{POST} || sub {
        my $val = shift;
        $val =~ s/FOO/BAR/;
        return $val;
    };
    return;
}

sub STORE {
    my ($self, $value) = @_;
    $value = $self->{PRE}->(  $value );
    $value = $self->{POST}->( $value );
    $self->{VAL} = $value;
}

sub FETCH { return $_[0]->{VAL} }


########################################

package cool;

sub new {
    my $class = shift;
    tie my $name, "magic", @_;
    bless \$name, $class;
}

sub name :lvalue {
    ${$_[0]};
}

########################################

package main;

tie my $string, "magic";
$string = 'My left foot';
print "$string\n";

my $obj = cool->new( 'POST' => sub { return reverse $_[0] } );

$obj->name = "My right foot";
print $obj->name, "\n";