Whoa! That's a strange undertaking. I hope it's only an academic exercise. In any case, accessing raw memory is largely what Perl is designed to shield you from. So as far as core Perl is concerned, you can't do that (and shouldn't be able to). A quick search didn't turn up an existing module to do this, but you could write a small XS extension (a Perl module written in C) which had routines to read to and write from specific memory locations, and then just call those in your program. Keep in mind this would most likely be insanely slow. But perhaps you could accelerate Commander Keen :-).

As far as the printing goes, you might not be far off. Provided your /dev/lp0 is configured to correctly handle raw text dumped to it, you should be able to use what you have if you make the handle writable (open(PRINTER,'>>/dev/lp0')) before printing to it. You may need to figure out how to send a page-feed, though, or just press the button yourself on the printer.