public function get($identifier)
    {
        switch ($identifier) {
            case '_all':
                return $this->variables;

            case 'true':
            case 'on':
            case 'yes':
                return true;

            case 'false':
            case 'off':
            case 'no':
                return false;
        }

        if (!array_key_exists($identifier, $this->variables)) {
            throw new InvalidVariableException('Tried to get a variable "' . $identifier . '" which is not stored in the context!', 1224479370);
        }
        return $this->variables[$identifier];
    }