Quick, dirty but typographically resilient UUID codes. Hex digits A, B, C, D, E and F are replaced by letters that cannot be mistaken by any digit or any other letter. The choosen letters are E, J, N, P, V and X.

my_uuid_codes.rb

# Takes 3 optional params: an int code_length, a string "separator" and a look-up "table" (hash).
def my_uuid_code(
  code_length = 24, 
  separator: '-',
  table: { "0" => '0', "1" => '1', "2" => '2', "3" => '3', "4" => '4', "5" => '5',
    "6" => '6', "7" => '7', "8" => '8', "9" => '9',
    "A" => 'E', "B" => 'J', "C" => 'N', "D" => 'P', "E" => 'V', "F" => 'X' })

  posibilities =  16**code_length
  
  return rand(posibilities).to_s(16).upcase.rjust(code_length, '0').chars.map { |digit| 
      table[digit] }.join.scan(/.{1,4}/).join(separator)
end