I can't, because if I fix the problem you mention, then the problem I describe in this post both disappears in the chopped version of my code posted here, and in the real, full version.

Below is a patched exception.t that completely fixes my problem, because by fixing the bug you mentioned, it also fixed the bug I though I was having. Unfortunately, it was foolish enough, and I was too frustrated to spot it before posting here for help. JavaFan thanks for pointing out my stupid mistake, because I really did think I was having the problem I previously described.

#!perl
# exception.t tests all of Exception.

use strict;
use warnings;
use diagnostics;
use 5.010;

use Test::More;# tests => '19';

BEGIN { use_ok('Exception', 'create_exception'); }

# Test uneven params.
# create exception w/params
create_exception('ParameterException', 'description', 'param', 'param2
+');
evalok(sub {eval {die Exception->throw('ParameterException', param =>)
+};},
    <<EOD, 'check throw()ing uneven params');
You tried to throw an exception that had an uneven number of parameter
+s and
their values.  The list of parameters you provide must be an even numb
+er of
parameters followed by their values as in a hash. (ex: 'exception' a =
+> '1', b
=> '2', c => '3')
EOD

done_testing();

# runs code, and validates the $@ error message.
# Why make people install Test::Exception if this little bit of code i
+s all
# that's needed?
sub evalok {
    my ($code, $expected_message, $test_name) = @_;
    $code->();
    my $croak = $@;
    $croak =~ s/\sat.*\n$//; #remove cruft.
    is($croak, $expected_message, $test_name);
}
[download]

The fix was simply creating the exception with create_exception() before trying to throw it. In the previously posted code, I though I was, but it was creating an exception named ParameterException, but using an exception named TestException.

JavaFan, I feel kinda foolish for posting code that doesn't even have the problem I think it does. Anyway, thanks for the extra set of eyes that made this nightmare I wasted hours debugging seem trivial and foolish. I guess this is what I get for creating new tests by copy and pasting code from previous tests, and forgetting to change all of the variables for the new code.