$re = '/^\{\s*run(?:\s+-(?<flags>[a-z]+(?:\s*-[a-z]+)*))*\s+(?<files>[\w.]+(?:\s+[\w.]+)*)\s*\}$/m';
$str = '{ run }
{ run file1 }
{run -abc file1.foo file2.bar }
{ run -ab -ogg -fgg file1.baz file2}
{run -f-a-ob file1 file2.biz}
';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
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