How can I show up a variable in template headinclude from the plugin global_start? I do not have created any custom template like my_custom_template shown in the code. Please advice me how can I put the variable $car in headinclude. Thanks!

plugin global start
$car ='Porsche';
$templater = vB_Template::create('my_custom_template');
$templater->register('car', $car);
$car = $templater->render();

template: headinclude
(...)
{vb:raw car}
(...)


Why doesn't it work? Thanks!