I brain coded a very similar click minimising gallery also in perl, in the early 2000s. The model of "click on image to go to next image" is what reminded me of my own.

I think my last iteration added fake film sprocket decor to the thumbnails. I enjoyed doing that. No idea what I did with the code, Loved seeing this and I am sure the OPs version is both better, more supportable, and very probably more performant and less bug ridden.