package Package1;

use base 'Exporter';

our @EXPORT_OK = qw/this that/;
our %EXPORT_TAGS = ( all => [qw/this that/], );

sub this { 'this' }

sub that { 'that' }

1;

##</code><code>##

package Package2;

use base 'Exporter';

use Package1 ':all';

our @EXPORT_OK = ( @Package1::EXPORT_OK, 'foobar' );
our %EXPORT_TAGS = %Package1::EXPORT_TAGS;
push @{ $EXPORT_TAGS{all} } => 'foobar';

sub foobar { 'foobar' }

1;