Abundant regex: Remove unnecessary prime test; length-=11

This results in a significant speed-up, undoing the slowdown resulting from commit 9ee4afd10844e63d7df710b39ee123aadf5836d1.

This is essentially the same change as was done in commit a1b19c6950aab33baa39c253a8b121bca17a2ad7 to the slower version.