iso646.h -- yet another reason we can't have nice things. At least it's not {di,tri}graphs.

iso646_facepalm.c

#include <stdio.h>
#include <iso646.h>

int main() {
    if (1 == 1 and 1 not_eq 2) {
        printf("It's nice that it got here, but it still compiled.\n");
    } else {
        printf("Everything is awful, forever\n");
    }
    return 0;
}