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( 1, 2, undef, undef,     5 )
( 1, 2,     3,     4, undef )

( 1, 2, undef, undef, undef )
( 1, 2,     3,     4, undef )

(parent, sally, tom)
(parent, bill, tom)
(parent, tom, sue)
...
(male, bill)
(male, tom)
(male, tim)

(
  <father, $person>,
  (parent, $person, $anyone),
  (male, $person)
)

#!/usr/bin/perl
use strict;
use warnings;
...
__END__
father bill
father tom