A hashing function is a function that takes input (usually a string) and gives back a number in some range.

A hash lookup algorithm takes keys, passes the keys to a hashing function, and then uses that number to select a bucket, then stores the key/value in the bucket in some way. Hopefully the keys are pretty much randomly distributed so each bucket has few things in it. Details vary, there are different hashing algorithms you can use, different ways to store things in buckets, often there is some dynamic decision on how many buckets to use, etc.

Perl's hashes are called hashes because they use a hash lookup algorithm to store data. That is why lookups are fast. But when you ask for them back (with keys or values) it just walks the buckets, and returns things out of the buckets. The order you get back depends on all sorts of things, starting with the hashing function and number of buckets...

As a test, anyone who can understand Re: Re: Shift, Pop, Unshift and Push with Impunity! probably understood this explanation perfectly.

Anyways, the order that stuff comes back is entirely determined by internal details, looks random, but isn't. So if you figure out what order keys will give for (for instance) a series of numbers, then just put the values in matched to where you want them to go and voila! You get output sorted from values just right for no apparent reason! :-)