.vimrc

" Highlight Ruby 1.8.x hash rocket
" This will prevent you to ever write it again
highlight ObsoleteHashRocket ctermbg=red guibg=red
au ColorScheme * highlight ObsoleteHashRocket guibg=red
au BufEnter * match ObsoleteHashRocket /=>/
au InsertEnter * match ObsoleteHashRocket /=>/
au InsertLeave * match ObsoleteHashRocket /=>/

convert_hash

#!/usr/bin/ruby
Dir['**/*.{rb,erb}'].each do |filename|
  content =  File.read(filename)
  File.open(filename, "w"){ |f| f.write content.gsub(/:([a-z0-9_]+)\s?=>/, "\\1:") }
end