Another alternative is to tie() your hash to a berkely db with DB_File.

use strict;
use DB_File;

my %cords;
tie %cords, "DB_File", "file_name";

if (!defined($cords{10000}))
{
    # generate %cords hash again
    ...
}
[download]

Update: The Silent Monk crazyinsomniac reminds me that DB_File doesn't support complex data structures. You can't store something like an array ref in a Berkeley DB.

-Matt