Arrows are not drawn

This might be a problem between the keyboard and chair, but if so, I'd say it suggests an issue with the documentation.

After reading https://metacpan.org/pod/PDL::Graphics::Gnuplot#arrow-place-an-arrow-or-callout-line-on-the-plot I attempted to draw an arrow on a plot, but nothing was drawn. I can get the similar label to work as expected, but not arrow. See below for an illustration:

use PDL;
use PDL::Graphics::Gnuplot;

my $win = gpwin;
$win->plot(
    {
        # This works
        label => [
            [
                'start',
                at => [ 25, 'graph(0.5)' ],
                'center',
            ],
            [
                'end',
                at => [ 75, 'graph(0.5)' ],
                'center',
            ],
        ],

        # This doesn't
        arrow => [
            [
                from => [ 25, 'graph(0.5)' ],
                to   => [ 75, 'graph(0.5)' ],
            ],
        ],
    },
    sequence(100) ** 2,
);

$win->pause_until_close;

This is the resulting plot, with the labels but no arrows:

Is this a bug in PDL::Graphics::Gnuplot? Or am I missing something?