See League.php : class League extends AbstractController, public function indexMethod()
<pre>return parent::getView(
    __METHOD__ ,
    [
        'title' => MODULE_NAME.' - Home',
        'header' => 'League list',
        'league_list' => 'A B C',
    ]
);

AbstractController calls template->getView so :
return $this->template->getView($controller, $variables);

    public function getView($controller, array $variables = [])
    {
        $variables = $this->validateVariables($variables);
 
        $parts = explode('::', $controller);
        $directory = $this->getDirectory($parts[0]);
        $file = $this->getFile($parts[1]);
 
        $viewPath = $this->viewPath.'/'.$directory.'/'.$file.'.html';
        if (file_exists($viewPath)) {
            $baseView = file_get_contents($this->viewPath.'/'.$this->baseView);
            $body = file_get_contents($viewPath);
            $view = str_replace('{{ body }}', $body, $baseView);
 
            foreach ($variables as $key => $value) {
                $view = str_replace('{{ '.$key.' }}', $value, $view);
            }
 
            return $view;
        }
 
        http_response_code(404);
        throw new Exception(sprintf('View cannot be found: [%s]', $viewPath), 404);
    }
</pre>
<br />{{ whoami }} league_list of Football Leagues is : 

<h2>{{ league_list }}</h2>