Constants are just subs. You can export them like any other sub

package Constants;

use strict;
use warnings;

use Exporter;
our @ISA = 'Exporter';

my %constants;
BEGIN {
   %constants = (
      FOO => 1,
      BAR => 1,
   );
}

use constant \%constants;

our @EXPORT = keys(%constants);

1;
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The code following is a proof of concept that you may extend upon, I have two files, CheeseSpread.pl which has the variables and CreamIt.pl which uses the variables declared in CheeseSpread.pl. Note, the file boundaries are not synonymous with package boundaries so it is possible to declare the variables in one file and then access them from different files.

#!/usr/local/bin/perl
#title "Wish I could include global constants"
#CheeseSpread.pl
use strict;
use warnings;
package CheeseSpread;

BEGIN{
    our $name = "Mary";
    our $monkish = "MaryFranan";
    }
1;
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#!/usr/local/bin/perl
use strict;
use warnings;
require 'CheeseSpread.pl' #imports the package symbol table;

print name();
print monkish();

sub name{
        return "my name is $CheeseSpread::name\n";
        }
sub monkish {
        return "my avatar is $CheeseSpread::monkish\n";
        }
print "-" x 50, "\n";   # a horizontal rule

my $firstName = $CheeseSpread::name;
my $monasteryName = $CheeseSpread::monkish;
print "my name is $firstName\n";
print "my avatar is $monasteryName\n";
1;
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%h2xs -X -A -n Name::Module
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