#!/usr/bin/perl

use strict;
use Net::SSH2;
my $hf = 'list.txt';
my $user = 'user';
my $pass = 'pass';
my $ssh = Net::SSH2->new();
$ssh->debug(1);
open (L,"<$hf") || die "$!";
while(<L>) {
  chomp $_;
  print "Connecting now..\n";
  $ssh->connect("$_") || warn "$!";
  $ssh->auth_password("$user","$pass");
  my $chan = $ssh->channel();
  $chan->exec('dir');
  $chan->close();
}
close L;

##</code><code>##

# ./test.pl
Connecting now..
libssh2_channel_open_ex(ss->session, pv_channel_type, len_channel_type, window_size, packet_size, ((void *)0) , 0 ) -> 0x841ed400
Net::SSH2::Channel::DESTROY
Connecting now..
Resource temporarily unavailable at ./test.pl line 14, <L> line 2.
libssh2_channel_open_ex(ss->session, pv_channel_type, len_channel_type, window_size, packet_size, ((void *)0) , 0 ) -> 0x0
Can't call method "exec" on an undefined value at ./test.pl line 21, <L> line 2.
Net::SSH2::DESTROY object 0x8663b6c0