a 3D shooter like quake wouldn't give enough frames per second to be comfortable enough on a common PC

If it was limited to using the CPU only, the recent Quake games couldn't work in C/ASM, either. You have to offload operations to dedicated 3D hardware to get Quake-level graphics. You need underlieing library support to take advantage of GPUs, which Perl has.

In the game I've been writing in Perl (2d sprites, not 3d), the biggest CPU-hog is collision detection. I'm using a rather naive algorithim (every object tested against every other object), so it does a lot more work than it needs to. With offloading some of the calculations into C code, the game is playable on my 2.2 GHz Celeron laptop (but only just so in some spots). In pure Perl, it's easily playable on my Athlon64 3200+ (2.0 GHz) desktop.

Fortunately, collision detection shouldn't be difficult to paralleize (at least from what I've seen so far), so this is an area that can take advantage of multicore processors. Also, there has been some research on using GPUs for collisions.