# File lib/facet/string/last%3D.rb, line 13
  def last=(str, separator=$/)
    separator = /\n+/ if separator == ''
    separator = /\s+/ unless separator
    separator = Regexp.new( Regexp.escape( separator ) ) if String === separator
    i = self.rindex(separator)
    return nil unless i
    self[$~.end(0)..-1] = str
  end