Are Java and C# regular expressions compatible?

Question

Both languages claim to use Perl style regular expressions. If I have one language test a regular expression for validity, will it work in the other? Where do the regular ex

Answer 1

.NET Regex supports counting, so you can match nested parentheses which is something you normally cannot do with a regular expression. According to Mastering Regular Expressions that's one of the few implementations to do that, so that could be a difference.