use strict;
use warnings;
use v5.010;


package PARENT;

use constant PARENT_ONLY => 23;
use constant BOTH => 42;

package CHILD;

use base 'PARENT';
use constant CHILD_ONLY => 99;
use constant BOTH => 42.1;

for my $name (qw/ PARENT_ONLY BOTH CHILD_ONLY /) {
    if (my $coderef = __PACKAGE__->can($name)) {
        my $result = $coderef->();
        say "CHILD->can($name), result=$result";
    }
    if (my $coderef = UNIVERSAL::can(__PACKAGE__, $name)) {
        my $result = $coderef->();
        say "UNIVERSAL::can(CHILD, $name), result=$result";
    }
}

CHILD->can(PARENT_ONLY), result=23
UNIVERSAL::can(CHILD, PARENT_ONLY), result=23
CHILD->can(BOTH), result=42.1
UNIVERSAL::can(CHILD, BOTH), result=42.1
CHILD->can(CHILD_ONLY), result=99
UNIVERSAL::can(CHILD, CHILD_ONLY), result=99