As my older projects get moved into the new world order, I find the need to clean up and stop using hashrocket syntax in ruby.
Here's my emacs function to help me out.
(defun convert-hashrockets ()
"Replace ruby hashrockets with new hash syntax"
(while (search-forward-regexp ":\\([-_A-Za-z0-9]+\\)[[:space:]]=>" nil t)
(replace-match ( concat (match-string 1) ":") t nil )))