Inline.pm is the coolest thing ever. After reading perlapi/perlguts again the other day (but this time seriously), I was able to bang out a C version of LJ's S1 style engine. [description in lj_dev]
I'm just so amazed it was so easy. I tend to fear things too easily, then kick myself later for not learning it earlier when I find out it wasn't hard at all.
Sorry those of you reading this in 3 places. :P