Others have mentioned MD5, but I also have to ask: Are you sure the "out of memory" error doesn't indicate a problem somewhere in your code? 500 hash keys by 1000 chars each seems unlikely to cause problems unless the values associated with each key are truly huge.

To test, I just wrote a program that generates 500 hash keys, each key a string of 1000 random characters, and each value a string of 1 million random characters, and it seems to work fine.

If you are still having problems after reading the suggestions on this thread, you might post some of your code to see if anyone can provide more specific help.

        $perlmonks{seattlejohn} = 'John Clyman';