I tried a variation of that using pack and unpack, but it was unworkably slow. I do need quick access to all the fields. It did save a fair amount of memory, but less than I would have hoped.

What I'm starting to envision is a somewhat-specialized XS module that builds something similar (I could afford pointers to the individual field strings) in C, and then allows access to it via XS. The db is read-only once it's sorted, so updates aren't an issue. You could malloc large blocks and just write null-terminated strings to them, updating the pointers for the fields.

But I know almost nothing about XS and whether the conversion from a string in C to what perl thinks is a string would be painfully slow. I would guess not, since it must do it internally all the time?