# File lib/facets/core/hash/rekey.rb, line 26
  def rekey!( meth=nil, &block )
    meth = :to_sym unless meth or block
    raise ArgumentError, "2 for 1" if meth and block
    block = meth.to_sym.to_proc if meth
    keys.each do |k|
      nk = block[k]
      self[nk]=delete(k) if nk
    end
    self
  end