$foreigner{abdul} = 1;
$foreigner{marcus} = 1;
$spouse{edward} = "sally"; $spouse{sally} = "edward";
$spouse{bill} = "hillary"; $spouse{hillary} = "bill";
$gross_income{hillary} = 100_000;
$gross_income{edward} = 20_000;
$gross_income{bill} = 30_000;
$gross_income{marcus} = 49_999;
$gross_income{mary} = 35_000;

sub average_taxpayer {my $Person = @_ ? shift : $_;
    !$foreigner{$Person}                and
    not ($spouse  = $spouse{$Person}        and
         $income1 = $gross_income{$spouse}  and
         $income1 > 30_000)                 and
    $income2 = $gross_income{$Person}   and
    $income2 < 50_000
}