I asked Twitter nicely yesterday. The only response:

I don't dislike writing bash scripts. I hate it. I also hate the lack of portability, as pointed out by +Daniel Steigerwald:

Great idea, +Daniel Steigerwald, but why use NodeJS when I could use Dart?

If you fetch the latest version of the Dart Bag-of-Tricks, you'll notice a new binary bin/bench.

If you're running bash and dart is in your path you can execute this directly. Otherwise run it through dart: dart bin/bench.

If you add bot.dart/bin to your path you can do things like this:
There is also a paramater -r, --run_count    (defaults to "20")

Dart is more than just a good tool for web apps.

Happy hacking.