#!/usr/bin/perl

use strict;
use warnings;

use Net::SFTP::Foreign;
use Fcntl ':mode';

my $host = 'localhost';
my $dir = shift @ARGV;

my $sftp = Net::SFTP::Foreign->new($host);

$sftp->find($dir,
            ordered => 1,
            wanted => sub {
                my (undef, $entry) = @_;
                if (S_ISREG($entry->{a}->perm)) {
                    my $fn = $entry->{filename};
                    $sftp->rename("$fn", "$fn.bak");
                }
                0;
            },
           );