Looping through 49,000 characters took our tail-recursive custom function almost 3 seconds.
And thanks to the improved fmp url in FileMaker 13, we can grab the results of functions like these quite easily. The movie below demos this and walks through our example file. It also gives a nice side-effect-demo of how webviewers get their own thread in FileMaker Pro and what that may mean for trying to measure performance.
There's a video at the link, also. The increase in speed and capability over native FileMaker is impressive!