1. Please use <code> tags. Without them your code is very hard to read. Fixed now.
2. To what box do you refer?
3. I can only guess that this is a scoping problem. Try declaring your variable first.

my $location_id;
if ($resp->is_success) { $location_id = $resp->header( 'Location' ); }
print $location_id;
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Update: Now that the code is legible it is easy to see that you have declared $location_id twice in the same block. If you had used warnings this would have been alerted to you. Don't double-declare.