fix-macos-brew-irb-arrow-keys.sh

# # Fixing key bindings for `irb` 
# 
# when your ruby comes from `brew`, `rbenv`, and arrow keys don't work in your `irb` 

brew upgrade readline rbenv ruby-install  # ensure we have the `readline` library, and a recent version of `ruby-install` which will link to it properly when building `ruby`.
rbenv install <your-favourite-ruby-version>  # rebuild ruby.

# watch out for the message 'ruby-build: use readline from homebrew' in output from the command above, 
# then, go get some coffee.
# ...

# and eventually, check that the arrow keys work in irb.
irb

Many thanks from me as well!