$re = '/^\.$/';
$str = '10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 000.0110, 120, 130, 260, 330';
$subst = "$1";
$result = preg_replace($re, $subst, $str, 1);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php