{ package Fake;
	sub present {
		my $class = shift ;
		print $class->head, "\n";
	}
	sub ack {
		my $class = shift;
		print $class->ok,"\n";
	}
	sub rst {
		my $class = shift;
		print $class->quit,"\n";
	}
}
{ package Ssh;
	@ISA = qw{Fake};
	
	sub head {
		my @fake = ("SSH-2.0-OpenSSH_3.8.1p1","SSH-2.0-OpenSSH_3.7p1","SSH-2.0-OpenSSH_3.5p1");
		$size = @fake;
		$rand = 0;
		$rand = int(rand $size);
		return $fake[$rand];
	}
	sub quit {return "Protocol mismatch."}
}


##</code><code>##

 
bind($port, 'Ssh');

sub bind ( $$){
my $port = shift;
my $obj =shift
......

}