After searching examples/solutions on internet, I decided to post my issue here to understand and try to solve my issue.
I am writting a perl script to upload big binary files (> 30 mo) to a file server using a Web Service.
I must POST my file(s) in a multi-part format.
To do so, I am using the LWP::UserAgent, HTTP::Request and Http::Response perl libraries. I am using a callback to read the file by chunk.
To write my 'upload' script, I took help from http://www.perlmonks.org/?node_id=761560 and https://labs.consol.de/blog/misc/fileupload-with-perl-decorated-with-a-progressbar/

Here my script section that processes the POST :

sub upload {
    my ($url, $binary) = @_;
    
    local $HTTP::Request::Common::DYNAMIC_FILE_UPLOAD = 1;
    
    my $ua = LWP::UserAgent->new(
        timeout => 10*60
    );
    
    my $request = POST ${url},
        'Content_Type' => 'form-data', 
        'Content' => { 'file_to_upload' => ["$binary"] };
    
    my $reader = &create_content_reader($request->content(),
                                        $request->header('Content_Leng
+th'));
                                        
    $request->content($reader);
    my $response = $ua->request($request);
    
    print STDOUT $response->status_line, "\n";   

    if ($response->is_success) {
        return JSON::decode_json($response->decoded_content); 
    }
    
    return undef;
}
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sub create_content_reader {
    my ($gen, $len) = @_;

    my $size = 0;
    my $next_update = 0;
    return sub {
        my $chunk = &$gen();
        $size += length($chunk) if $chunk;
        return $chunk;
    }
}
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My issue is when the file is less than 30 Mo, my script is running like a charm but, > 30Mo, I have got a "404 Not Found" error message as response.
Why ?