from node in new HtmlWeb().Load("http://regex.alf.nu/").DocumentNode.SelectNodes("//script")
let script = node.InnerText
let json = Regex.Match(script, @"levels = (\[.+?\]);", RegexOptions.Singleline).Groups[1].Value
let fixedJson = Regex.Replace(json, @"x\((\d+)\)", m => "'" + new string('x', int.Parse(m.Groups[1].Value)) + "'")
let levels = JArray.Parse(fixedJson)
let alphabet = @".[](){}*+-?!=^$\|<>".AsEnumerable()
    .Concat(Enumerable.Range('a', 'z'-'a'+1).Concat(Enumerable.Range('0', 10)).Select(c=>(char)c))
    .ToList()
let combinator = new Func<Func<int, IEnumerable<string>>>(()=>
{
    Func<int, IEnumerable<string>> combinator = null;
    combinator = length =>
        from start in length > 1 ? combinator(length - 1) : new[]{""}
        let combinations =
            from c in alphabet
            select start + c
        from combination in new[]{start}.Concat(combinations)
        select combination;
    return combinator;
})()
let sw = Stopwatch.StartNew()
from level in levels
let name = (string) level["name"]
let good = from word in level["good"] select (string) word
let bad = from word in level["bad"] select (string) word
let solutions = from pattern in combinator(5)
    let regex = new Func<Regex>(() => { try { return new Regex(pattern); } catch { return null; } })()
    where regex != null
    where good.All(word => regex.IsMatch(word))
    where bad.All(word => !regex.IsMatch(word))
    select pattern
select new { name, solution = solutions.FirstOrDefault(), elapsed = sw.Elapsed }.Dump()