It looks like you just have a little typo to me.. In TrialWorkers::DaySignup, you have:

TrialWorkers::DaySignup->has_a(people_id=>'TrialWorkers::People');
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Which should be:

TrialWorkers::DaySignup->has_a(people_id=>'TrialWorkers::Person');
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Thus Class::DBI is falling back to the default, and looking for a column with the name of the class, instead of the one that has_a tells it to use.

C.