If you are creating a module to include configuration information, you might find the following useful. Firstly, we create the module that holds the configuration information, making sure the proper things are exported. Source:

package Testing;

use strict;
use Exporter;

our @ISA = qw(Exporter);
our (%EXPORT_TAGS);

$EXPORT_TAGS{'config'} = [qw($verbose $debug)];
Exporter::export_ok_tags('config');

our ($verbose, $debug) = (1,1);

1;
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And the main script that exploits the configuration information:

use strict;
use warnings;
use Testing qw(:config);

print "I am ", $verbose ? "" : "not ", "verbose\n";
print "I should ", $debug ? "" : "not ", "debug\n";
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When the code directly above is run, it produces, as expected:

I am verbose
I should debug
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For instance, if we changed this line ( our ($verbose, $debug) = (1,1); ) in the configuration module, to ( our ($verbose, $debug) = (undef,undef); ) we would get:

I am not verbose
I should not debug
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