class Net::POP3

end
....
pop.start(account, passwd) do |pop|
pop.set_debug_output $stderr
pop = Net::POP.new(addr, port)

=== Example

Set an output stream for debugging.

Use this method only for debugging.
*WARNING*: This method causes a serious security hole.

def set_debug_output(arg)
  @debug_output = arg
end