Regexes match from left to right. So, if you first say "match /*", and then say, "don't match throw", it's *not* going to exclude "/*"'s that are preceeded with "throw". In fact, you haven't given any requirements for what should preceed "/*".
Ignoring the fact that you don't specify what should happen on a line like this:
you might want to use something like:/* throw /*
although that can probably be optimized (and the more you know about where you are going to match against, the more possibilities for optimizing there are).m!^(?:(?!throw).)*/[*]!s