examples/Moose/person02/script/person.pl
use strict;
use warnings;
use v5.10;

use Person;

my $student = Person->new( name => 'Foo' );

$student->year(1988);

say $student->year;

$student->year('23 years ago');
examples/Moose/person02/lib/Person.pm
package Person;
use Moose;

has 'name' => (is => 'rw');
has 'year' => (isa => 'Int', is => 'rw');

1;

examples/Moose/person02/err.txt
Attribute (year) does not pass the type constraint because:
   Validation failed for 'Int' with value "23 years ago"
       at accessor Person::year (defined at lib/Person.pm line 5) line 4
   Person::year('Person=HASH(0x19a4120)', '23 years ago')
       called at script/person.pl line 13