Still, I'd point out that your "Next", "Previous" and "Delete Entry" buttons have a lot in common among their respective "-command" callback subs, so you'd be better off writing an actual sub that takes a parameter for each mode of operation, and set the "-command" options to something like [\&manip_entry, 'next'] etc. Eliminating redundant lines of code is always a good thing.

Apart from that, I would also suggest that consistent and logical indentation is always worthwhile. The pattern you have in the "display_text" sub is especially gruesome and somewhat misleading.