#!/usr/bin/perl
use strict ;
use warnings ;
use CGI ;
use Net::FTP;

my $cgi = CGI->new();

...

my $file_name = $cgi->param( 'doc' ) || '';
$cgi->upload( 'doc_upload' );

# Can I alter where the file is temporally written here?
my $tmp_file = $cgi->tmpFileName( $file_name );

##</code><code>##

 warn qq{rename ("$tmp_file", "temp/$file_renamed");\n};
 if (!rename("$tmp_file", "temp/$file_renamed" )) {
  warn $!, "\n";
}
chmod 0664, "tmp/$file_renamed";

# Error:
#Cannot open Local file doc1.txt: No such file or directory

##</code><code>##

 rename ("", doc1.txt");

##</code><code>##

...
#my $put_file = $ftp->put("$file_renamed") or die "Cannot put file ", $ftp->message;
...
Error : Cannot put file The system cannot find the file specified.