How about variables that contain constant values

Simply build a function that returns the variables.

You could, but it's perfectly fine to export constants. I'd make them look like constants, though. In fact, I don't see why we couldn't make them actual constants.

package PkgA;

use strict;
use warnings;

use Exporter qw( import );

my %max_text_constants;
my @max_text_constants;
BEGIN {
   %max_text_constants = (
      TINY_TEXT_MAX_LEN   =>  100,
      TEXT_MAX_LEN        =>  200,
      MEDIUM_TEXT_MAX_LEN =>  500,
      LONG_TEXT_MAX_LEN   => 2000,
   );

   @max_text_constants = keys(%max_text_constants);
}

use constant \%max_text_constants;

our @EXPORT_OK = (
   @max_text_constants,
   ...
);

our @EXPORT_TAGS = (
   max_text => \@max_text_constants,
   ...
   all      => \@EXPORT_OK,
);

1;
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use PkgA qw( LONG_TEXT_MAX_LEN );
use PkgA qw( :max_text );
use PkgA qw( :all );
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