In message "[ruby-talk:00869] Re: call with a Proc"
    on 99/10/28, ts <decoux / moulon.inra.fr> writes:

>G>   b.list(arg1, arg2, &Proc.new{ ... })
>
> OK, I've forgotten & before Proc

By the way, the error massage was not kind. It was difficult to 
realize the absence of &. 

I think FTP#list should do type-check and display more suitable
message if type error is detected. 

-- gotoken