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Phone numbers in Twilio’s API need to be formatted like this: +xxxxxxxxxx

In code this can be difficult to read and easy to make a mistake with. With Ruby you can run code against a constant string before it gets constantized (“pre-processing”): 

NUMBER = '+1 (777) 239-3636'.gsub(/[^0-9+]/, '')
puts NUMBER  #=> +17772393636
Now you can read a value in code, and clean it of extra characters before using it.