selective.rb

def proper(phrase)
  words = phrase.split(" ")
  words.map {|word| cap_if_selected(word)}.join(" ")
end

def cap_if_selected(word)
  word = word.each_char.map {|char| down_char(char)}.join
  word[0] = up_char(word[0]) if selected(word)
  word
end

def selected(word)
  word.length > 3
end

def up_char(char)
  up_hash = Hash[('a'..'z').zip('A'..'Z')]
  char.match(/[a-z]/) ? up_hash[char] : char
end

def down_char(char)
  down_hash = Hash[('a'..'z').zip('A'..'Z')].invert
  char.match(/[A-Z]/) ? down_hash[char] : char
end

p proper("word Of MOuth")

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