I've tried using the upload function. It returns undef, which, according to the man page, means the parameter is not a valid filehandle. But why not? I have a normal looking form field:

<input type="file" name="file_image" ...
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I've done the test according to your second quote. There's definitely nothing coming back from:

  my $handle_in = $cgi->upload('file_image');
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But it's not a POST_MAX problem. That's set to -1, which means no limit. There's a function called cgi_error(), but that's not returning anything either.