self + other -> String
文字列と other を連結した新しい文字列を返します。
例 p "str" + "ing" # => "string" a = "abc" b = "def" p a + b # => "abcdef" p a # => "abc" (変化なし) p b # => "def"
p "str" + "ing" # => "string" a = "abc" b = "def" p a + b # => "abcdef" p a # => "abc" (変化なし) p b # => "def"