I analyze data consisting of many items but little information per item. I quickly ran across perl's hunger for memory. In my experience (linux 2.2/perl5.6/gcc) perl asks for 43 byte overhead per item (that is just from total memory footprint with large lists in memory, so not really accurate). If your list has 10 million items, you need 400 megabyte of memory. That's simply too much.

There are solutions:

1. BerkeleyDB
2. pack/unpack bytestrings
3. vec on bitstrings

I conincedently started to use the latter one this week, and it works good. For large lists, I have to keep a few flags per item. vec returns or sets bits (the desired number of bits, actually) so you do not need pack conversions, and that really clears up the code.

For really large lists, BerkeleyDB is the way to go. Find it at http://www.sleepycat.com.

Cheers,

Jeroen
"We are not alone"(FZ)