LWP is Simple.

While I'm on the nerd tip, this is the simplest example I can get to grab the contents of a URL, with a optional username/password and/or proxy:

 
#!/usr/bin/perl 
 
my $proxy = undef; 
my $user  = undef; 
my $pass  = undef; 
my $url   = 'http://localhost'; 

 # Create a user agent object
 require LWP::UserAgent;
 my $ua = LWP::UserAgent->new;

 if($proxy){ 
  $ua->proxy(
   ['http', 'ftp'], 
   $proxy
  ); 
 }
 
 # Create a request
 my $req = HTTP::Request->new(
    GET => $url
   );
 # Pass request to the user agent and get a response back
 my $res = $ua->request($req);
 if(
   defined($user) && 
   defined($pass)
 ){ 
    $res->authorization_basic(
   $user, 
   $pass
  );
 }
 # Check the outcome of the response
 if ($res->is_success) {
     return $res->content;
 }
 else {
     warn $res->status_line;
  return undef; 
 }
}

Wishing LWP::Simple would do this, but. Nope.

MIME Trickery with MIME::Parser and friends

You can attach attachments to a multipart/related email message entity (say, a email message created from a website, with the images attached to the message itself) by creating a new multipart/mixed entity, and having the first part be that multipart/related entity and the rest being your new attachments. For example:

 
#!/usr/bin/perl 
use strict; 

use :MyMIMELiteHTML; 
use MIME::Parser; 
use MIME::Entity; 

my $HTMLurl = 'http://localhost'; 
my $jpg_path = '/Users/justin/Desktop/4.jpg';


my $mailHTML = new MyMIMELiteHTML(
 'IncludeType' => 'cid', 
); 
                 
my $MIMELiteObj = $mailHTML->parse($HTMLurl)  ;

 
my $msg_as_string =  $MIMELiteObj->as_string; 


my $parser = new MIME::Parser;

my $entity = $parser->parse_data($msg_as_string);


# Attach stuff to it:


my $cont_entity = MIME::Entity->build(Type        => "multipart/mixed");
   $cont_entity->add_part($entity); 
   $cont_entity->attach(
    Path     => $jpg_path,
                Type          => "image/jpg",
                Encoding      => "base64",
    Disposition   => "attachment",
    );

print $cont_entity->stringify;

MyMIMELiteHTML is just my version of MIME::Lite::HTML, with a few bug fixes and changes to fit in my program better.

http://search.cpan.org/~alian/MIME-Lite-HTML-1.22/HTML.pm

I've tried also just added the attachments to the multipart/related entity, but the new attachments never can be found - at least in Mail.app (Gmail? Yes?), unless you put in a bogus Content-ID header for the attachement - which actually could come in handy in some rare cases, but I digress...