how to read the global in volt

I see the doc: {{constant()}} Reads a PHP constant

But it can not read the value of global...
i set : global $_W;$_W['TR'] = 'Phalcon';

I want to read the value in volt ,how  to write in volt ??

Just don't use globals ? Why you even need them ?

$this->view->setVar('TR', 'Phalcon');
{{ TR }}

Will return Phalcon.