See the documentation for
Exporter. Basically anything you list in
@EXPORT_OK will be available for import by name into other modules which
use the exporting module, and anything you list in
@EXPORT will be imported automatically into
useing modules. It's generally considered better style to use
@EXPORT_OK, or to use a named tag in
%EXPORT_TAGS, but if the whole purpose of your module is to provide constants
@EXPORT may be OK.
Your module might look something like this:
package MyConst;
use warnings;
use strict;
use base 'Exporter';
use vars qw(@EXPORT_OK %EXPORT_TAGS);
@EXPORT_OK = qw($const1);
%EXPORT_TAGS = (all => \@EXPORT_OK);
# ...
And the module using it would begin like this:
use MyConst qw(:all);