This is how I read:

is_contact_female?;     # interogative, expect yes or no.
contact_is_female;      # declarative, assume the contact is female.
contact_become_female;  # imperative, make contact female.
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The reason I don't like $contact->is_female is that I read it as "the contact is female". However, if I were able to say $contact->is_female?, well, that is a piece of sugar that I'd eat.