I've run across the same thing in DBI with postgresql's bool type. It has lead to some really odd looking code:

sub is_purple {
  ...
  return $color eq 'purple' ? '1' : '0';
}
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The return value is destined to be bound into a SQL statement, and a more natural set of true/false values simply doesn't work. In most cases, I would redflag a line such as that, but in this one weird case it actually makes sense.

-Blake