#!perl
package Example::Constants;

use Exporter qw( import );
use Readonly;

Readonly my $EMPTY_STRING => q{};
our @EXPORT = qw( $EMPTY_STRING );

#!perl
use Example::Constants;
print $EMPTY_STRING . 'foo' . $EMPTY_STRING;

Readonly our $EMPTY_STRING => q{}; # 'our' instead of 'my'

package Example::Constants;

use strict;
use warnings;
use base 'Exporter';
use Readonly;

Readonly our $EMPTY_STRING => q{};
our @EXPORT = qw( $EMPTY_STRING );

1;

#!perl
package Example::Constants;

use Exporter qw( import );
use Readonly;
use Scalar::Util qw(readonly);

our $EMPTY_STRING;
our @EXPORT = qw( $EMPTY_STRING );

if ( !readonly( $EMPTY_STRING ) ) {
    Readonly $EMPTY_STRING => q{};
}

#!perl
package Example::Constants;

use Exporter qw( import );
use Readonly;
use vars qw( $EMPTY_STRING );

Readonly $EMPTY_STRING => q{};
our @EXPORT = qw( $EMPTY_STRING );

#!perl
package Example::Constants;

use Exporter qw( import );
use Readonly;

our $EMPTY_STRING;
*EMPTY_STRING = q{};
our @EXPORT = qw( $EMPTY_STRING );