public function propertyValue(&$value, $keyName = null) {
$values = array();

if ($keyName !== null) $this->env->currentProperty = $keyName;

$s = null;
while ($this->expressionList($v)) {
$values[] = $v;
$s = $this->seek();
if (!$this->literal(',')) break;
}

if ($s) $this->seek($s);

if ($keyName !== null) unset($this->env->currentProperty);

if (count($values) == 0) return false;

$value = \ATPCore\Lessc::compressList($values, ', ');
return true;
}