s = "hELLO!"
puts s.swapcase
puts toggle(s)

class String
def change_case
s2 = ''
each_char{|c| s2 << (c =~ /[A-Z]/ ? c.downcase : c.upcase) };
s2
end
end

class String
def change_case
split(//).map{|c|c=~/[A-Z]/?c.downcase: c.upcase}.join
end
end

class String
def change_case
gsub(/./){|c|c=~/[A-Z]/?c.downcase: c.upcase}
end
end

class String
def change_case
s.gsub(/./){|c|c.upcase!||c.downcase}
end
end


class String
def change_case
split(//).map{|c|(c[0]+((('a'..'z')===c ?-1:(('A'..'Z')===c ?1:0))*32)).chr}.join
end
end