Did you try using array.flatten instead of your customize array_concat.rb script?
Also array_concat is a bad name because concat is generally meant to combine two or more arrays to a single array.
More information here:
Try this instead puts a.flatten.join('')
Hiya. Sorry for the long delay. I didn't realise I had unread notifications.
I'm going to delete this script. You've made a great point: flatten does exactly what I want. Thanks a lot.