#!/usr/bin/perl
use JSON;
use strict;
use warnings;
use MIME::Base64;
use Data::Dumper;
use feature 'say';
use LWP::UserAgent ();
use HTTP::Request::Common;

my $ua = LWP::UserAgent->new;
$ua->timeout(10);
$ua->env_proxy;

my $url = "http://127.0.0.1:8000/upload/";
my $file = "test.txt";

$HTTP::Request::Common::DYNAMIC_FILE_UPLOAD = 1;

my $req = POST(
    $url,
    Authorization => 'Basic ' . encode_base64('user' . ':' . 'password'),
    Content_Type => 'multipart/form-data',
    Content      => [ file => [$file] ],
    );

my $res = $ua->request($req);   #do it
say $res->status_line;

my $response = $ua->get('http://127.0.0.1:8000/snippets/1/');

if ($response->is_success) {
    print Dumper decode_json($response->decoded_content);  # or whatever
}
else {
    die $response->status_line;
}

__END__

$ perl test.pl
201 Created
$VAR1 = {
          'highlight' => 'http://127.0.0.1:8000/snippets/1/highlight/',
          'url' => 'http://127.0.0.1:8000/snippets/1/',
          'id' => 1,
          'owner' => 'user',
          'code' => 'Test POST file Perl',
          'language' => 'perl',
          'title' => 'Default Title',
          'style' => 'emacs',
          'linenos' => bless( do{\(my $o = 0)}, 'JSON::PP::Boolean' )
        };