Thanks everyone for all your help! VSarkiss and tye mentioned it might be FORTRAN and it seemed like I'd read that somewhere already. I then went back and started to re-read the Standards for Digital Elevation Models, and in one of the appendices it list the column types as REAL*8 (FORTRAN Notation). So once again, the virtues of "RTFM" are made clearer to me. In the end, I simply substituted D for E and went on.
in reply to Weird number formatting
I happened to notice that it still wouldn't consider it a "number" until I performed some kind of math function on it, so I just added 0 and everything worked fine. So once again, thanks everyone!
$inrecord =~ s/D/E/g;
@info = split(' ', $inrecord);
$my_x = $info + 0;
$my_y = $info + 0;