I couldn't get $attr->does('Bool') to work with isa, so I took it out. This works, but is there a better way?

package MyCow;
use Moose;

has 'guernsey'  => (
    traits  => ['Bool'],
    is      => 'rw',
    isa     => 'Bool',
);    

my $cow = MyCow->new;
$cow->guernsey(1);
print "How now, ",
    $cow->guernsey ? "brown" : "purple",
    " cow?", $/;

my $attr = $cow->meta->get_attribute('Bool');
print "Attribute does Boolean? ", $cow->guernsey ? "Yes!" : "No...", $
+/;
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