$intermediateStack = array();
foreach ($intermediateStack as $key => $value) {
    if ($key === 'tx_realurl') {
        $intermediateStack['my-before-realurl'] = 'My\\Extension\\Hooks\\RealUrl->beforeRealUrl';
    }
    $intermediateStack[$key] = $value;
    if ($key === 'tx_realurl') {
        $intermediateStack['my-after-realurl'] = 'My\\Extension\\Hooks\\RealUrl->afterRealUrl';
    }
}
$GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['t3lib/class.t3lib_tstemplate.php']['linkData-PostProc'] = $intermediateStack;