#!/bin/perl
 
use Expect;
 
 
$host = xxxxx;
$user = yyyyy;
$pw   = shift;
 
#--- CONFIGURATION -----------------------------------------------------------#
$cmd    = "ssh -l $user $host";
$prompt = "[Pp]assword";
 
#--- START SSH LOGIN SEQUENCE ! ----------------------------------------------#
$exp = new Expect();
$exp->log_file("SSHLOGFILE.txt");
$exp->raw_pty(1);  
$exp->spawn($cmd);
 

$exp->expect(10,
               [ qr/\(yes\/no\)\?\s*$/ => sub { $spawn->send("yes\n"); exp_continue; } ],   
               [ $prompt => sub { $_[0]->send("pwd\n"); } ]);




Here im unable to switch to super user login 
$exp->send("su - root\n");
$exp->expect(10,
               [ $prompt => sub { $_[0]->send("pwd\n"); } ]);

$exp->close();