Try this. It prompts for a password. It returns true if correct or "Permission denied" if incorrect.

#!/usr/bin/perl

use strict;
no warnings;
use Expect;
use Net::OpenSSH;

select STDOUT;
$| = 1;
select STDERR;
$| = 1;

my $username = 'root';
my $password = $ARGV;
my $ip       = 'localhost';
my $timeout  = 10;
my $debug    = 0;

my $ssh = Net::OpenSSH->new( "$username\@$ip", 
                            strict_mode => 0 );

my ( $pty, $pid ) = $ssh->open2pty("show ip arp")
  or die "unable to run remote command show ip arp";

my $expect = Expect->init($pty);
$expect->raw_pty(1);
$debug and $expect->log_user(1);
$debug and print "waiting for password prompt\n";
$expect->expect( $timeout, ":" )
  or die "expect failed, $expect->exp_error()\n";
$expect->send("$password\n");
while (<$pty>) {
    print "$. $_";
}
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