One common hurdle Emacs users experience when hacking in Emacs is that many programming languages use CamelCase for class names, method names, identifiers, etc, but Emacs (unlike most IDEs) doesn’t treat CamelCase words the same special way it treats lisp-case and snake_case words. Let me illustrate this with an example.

If you invoke kill-word (M-d) when your cursor is before lisp-case this would kill just lisp and leave you with -case. If you do the same with CamelCase the entire “word” CamelCase will be killed. Same goes for navigation-by-word commands like forward-word, backward-word, etc - they are aware of the subwords that comprise a lisp-case or a snake_case word, but are oblivious to CamelCase. So, what can we do? The answer is surprisingly simple - just use the built-in minor mode subword-mode (formerly known as c-subword-mode).

;; enable just in ruby-mode
(add-hook 'ruby-mode-hook 'subword-mode)

;; enable for all programming modes
(add-hook 'prog-mode-hook 'subword-mode)

At this point you can try again kill-word before CamelCase. Only Camel is killed now. Sweet!

Prelude enables subword-mode out of the box for programming modes that make use of CamelCase.