The perils of use constant

gistfile1.txt

Mark@travis:~/tmp/nac$ ls  
MyClass.pm	MyConstants.pm	RoleA.pm	RoleB.pm
Mark@travis:~/tmp/nac$ cat MyConstants.pm 
package MyConstants;
use base qw(Exporter);

# this is fine
sub my_good_constant { 1 };
push @EXPORT_OK, qw(my_good_constant);

# this ain't
use constant my_bad_constant => 1;
push @EXPORT_OK, qw(my_bad_constant);

1;
Mark@travis:~/tmp/nac$ cat RoleA.pm 
package RoleA;
use Moose::Role;

use MyConstants qw( my_good_constant my_bad_constant );

sub from_role_a { return 1 };

1;
Mark@travis:~/tmp/nac$ cat RoleB.pm 
package RoleB;
use Moose::Role;

use MyConstants qw( my_good_constant my_bad_constant );

sub from_role_b { return 1 };

1;
Mark@travis:~/tmp/nac$ cat MyClass.pm 
package MyClass;
use Moose;

with 'RoleA', 'RoleB';

__PACKAGE__->meta->make_immutable;

1;
Mark@travis:~/tmp/nac$ perl MyClass.pm 
Due to a method name conflict in roles 'RoleA' and 'RoleB', the method 'my_bad_constant' must be implemented or excluded by 'MyClass' at /opt/markperl/lib/site_perl/5.22.0/darwin-2level/Moose/Exporter.pm line 419
	Moose::with('RoleA', 'RoleB') called at MyClass.pm line 4
Mark@travis:~/tmp/nac$