So maybe we're talking about something different?

$ua->default_header( $field => $value )

    This is just a short-cut for $ua->default_headers->header( $field 
+=> $value ). Example:

      $ua->default_header('Accept-Encoding' => scalar HTTP::Message::d
+ecodable());
      $ua->default_header('Accept-Language' => "no, en");
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So couldn't I do something like:

$client->transport->default_header( 'my_special_header' => 'sha1hash')
+;
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EDIT: hmm... this in the LWP doc confuses me,

request_preprepare => sub { my($request, $ua, $h) = @_; ... }

    The handler is called before the request_prepare and other standar
+d initialization of the request. This can be used to set up headers a
+nd attributes that the request_prepare handler depends on. Proxy init
+ialization should take place here; but in general don't register hand
+lers for this phase.
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Is it saying in the request_prepare is where I should set my headers, or is this merely an option? I can't tell if $client->transport->default_headers() is working. haha. Was working on exporting a pcap (I develop on a vm but have wireshark locally)

Thanks for all the guidance. I can't tell if my frustration is coming through in my posts (which usually means it is) but it certainly isn't directed at you Anonymous Monk. I really do appreciate your helping me through all this.

EDIT: Hahaha!!!! IT does work, it helps to spell the name of the key right!

$client->transport->default_header( 'properly-speleeed-key' => $value 
+);
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Does exactly what I want!!!