package MyDateTime;

use parent qw(DateTime);

sub is_leap_year {
    my $self = shift;
    my $ly = $self->SUPER::is_leap_year;
    return ($ly, ($ly ? 'intercalary' : 'standard'));
}

1;

package main;

use MyDateTime;

my $dt = MyDateTime->new(...);

my @ly = $dt->is_leap_year;

print "This is ", ($ly[0] ? 'leap ' : 'a normal '), "year, otherwise known as $ly[1]\n";