Very simple kirbytag

Hello
Just a simple question, i would like to make two custom kirbytags, one to display the last modified date, the other to get the kirby version. So I must use :

$site->modified('d.m.Y') ;
$kirby->version() ;

I could write something like (version : Kirby) and (site : modified) to get : 22.02.18 and <a href="https//getkirby.com">Kirby 2.5.8</a>

But I don’t know if I can echo something else than a $tag in a kirby tag…this is my try :

kirbytext::$tags['version'] = array(
  'html' => function($tag) {
    return '<a href="https://getkirby.com/">' . $tag->attr('version') . ''. $site->modified('d.m.Y') . '</a>';
  }
);
<?php
kirbytext::$tags['version'] = array(
  'html' => function($tag) {
    return '<a href="https://getkirby.com/">'.$tag->attr('version').' '.$tag->page()->kirby()->version().'</a>';
  }
);

And for the site:

$tag->page()->site()->modified($format);

Thanks ! I undestand the logic now !
Best