This is very useful, I used this module(just download and put into the perl site path) and completed the task.

my $private_key = $ENV{'APPDATA'}."\\ssh_key\\putty_gen_private_key.pp
+k";
$sftp = Net::SFTP::Foreign->new($server, 
                            user => $user, 
                ssh_cmd => 'plink', 
                more    => [ -i => $private_key]
                );
    $sftp->die_on_error("Unable to establish SFTP connection");
[download]

used put() methed to copy the files from windows to unix.