Just a few comments on this:

The code has no use strict;, but most of the variables appear to be lexicalised. Would it run under strict?

What is hkpcore, and where can you get it?

This may be a cool use of perl to you, but why? You present no accompanying documentation or POD. Who would use the code, what for and how?

I have an aversion to prototypes, and can see no reason why min3, max3, etc need them.

My $0.02