Full code review

[poddmo]

abcde is over 26 years old and has had many maintainers and contributors. The code could do with a review to improve readability, make it more efficient and amenable to change. For example:

• bash lint
  Run shellcheck abcde review and squash a few notices

• AI review
  Suggestions for breaking out recurring code into functions
  Model and prompt recommendations welcome

[poddmo]

I am interested. Let's see your full code review of abcde, covering:

Bash linting (shellcheck analysis)
Refactoring suggestions for recurring code
Performance improvements
Readability enhancements