def strip_string_array(arr)
      arr.first.lstrip! if arr.first.is_a?(String)
      arr[-1] = Sass::Util.rstrip_except_escapes(arr[-1]) if arr.last.is_a?(String)
      arr
    end
def strip_string_array(arr)
      arr.first.lstrip! if arr.first.is_a?(String)
      arr[-1] = Sass::Util.rstrip_except_escapes(arr[-1]) if arr.last.is_a?(String)
      arr
    end
Destructively strips whitespace from the beginning and end of the first
 and last elements, respectively, in the array (if those elements are
 strings). Preserves CSS escapes at the end of the array.

 @param arr [Array]
 @return [Array] `arr`