First, you are accumulating the frames in $gifdata .= $frame->gifanimadd;, but then you print just the header info from the image into the file: print F $img->gif();. You should be printing the accumulated headers and frame data to the file: print F $gifdata;

Silly me, of course, I was doing it wrong. It is all working now, many thanks. Oh, and GD is about an order of magnitude faster than Imager. This would make a significant difference when I work with real data... 100 years worth (iow, 100 frames) of a few hundred thousand to a couple of million cells.

That doesn't affect a complete fix though because you're also confusing what constitutes a frame and what a complete animation. That is, you appear to be drawing a complete set of moving rectangles into each frame, rather than one rectangle at a different position in each frame.

No, thankfully, I got that part right.

Now I have to figure out whether an animated gif is appropriate for me (pretty universal readability... all browsers can), or if I should go the route of HTML5 video. What I would really like is a user-controllable scrub/scroll bar so the time-lapse can be changed to any time period. But, that is not a perl problem...

Many thanks again.