$cursor->move_right(3); # move cursor three chars to the right
$cursor->move_down(); # move cursor one line downwards

# and

my $left_pos = $cursor->move_left(1);
# position one char to the left of the cursor

my $start = $cursor->start_of_document();

##</code><code>##

sub frobnicate_position {
    my ($self) = @_;
    my $obj;
    if (defined wantarray) {
        $obj = $self->copy();
    } else {
        $obj = $self;
    }

    ... calculate new position here,
    ... set $obj->line() and $obj->column()

    return $obj
};

##</code><code>##

sub positional_mutator(&;$) {
    my ($worker,$name) = @_;
    no strict 'refs';
    *{$name} = sub {
        my $self = shift;
        my $obj;
        if (defined wantarray) {
            $obj = $self->copy();
        } else {
            $obj = $self;
        };
        $worker->($obj,@_);
    }
};

positional_mutator {
  my ($obj,@args) = @_;
  ... calculate new position here
}, 'frobnicate_position';