*ponders* You're doing everything by 1-dim lists. Why not do your coordinate lists as a single 2-dim list? It'll be memory-intensive, but should lend itself to some rather neat possibilities.

For example, you could set the value of $plane[$x][$y] to 'S' for if it's shortlist-only, 'L' for longlist-only, and 'SL' if it's both.

In the simple case of 'SL', you know the closest one.

Otherwise, you would do a walk-about. Start by checking the four to the N, S, E, & W. Then, check the NE, NW, SE, & SW. And, then keep doing that, keeping in mind the very simple distance algorithm and how it's affected by number-over and number-up. You're doing sort of a radiating-out-from-the-center algorithm.

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/me wants to be the brightest bulb in the chandelier!

Vote paco for President!