The following code snippet illustrates the problem. I define two constants near the top and then use them in two different hash definitions. The first one comes out via Data::Dumper as I would expect but in the second one the constants are not converted to the values I want and remain as the constant labels.

use strict;
use warnings;
use Data::Dumper;

use constant E_MESYSTEM     => 1;
use constant E_MEENTITY  => 2;

my %element_type = (
    system                 => E_MESYSTEM,
    entity                 => E_MEENTITY,
);

my %generator_lookup = (
    E_MESYSTEM                  => 'G_SYSTEM_SYSTEM_ID',
    E_MEENTITY                  => 'G_ENTITY_ENTITY_ID',
);

print Dumper(\%element_type);
print Dumper(\%generator_lookup);

__END__

#Ouput correct
$VAR1 = {
          'system' => 1,
          'entity' => 2
        };
        
#Output incorrect
$VAR1 = {
          'E_MESYSTEM' => 'G_SYSTEM_SYSTEM_ID',
          'E_MEENTITY' => 'G_ENTITY_ENTITY_ID'
        };
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