Perl Security: 3. Reporting warnings
Warnings and modules

A module can be registered to be controlled more easily:

package This::Module;
use warnings::register;
sub testing {
     my $text = shift
    if (warnings::enabled() && $text=~/[abc]/) {
        warnings::warn('Text contains a, b or c.');
    }
}

And then, from the main program:

use This::Module;
use warnings 'This::Module';
This::Module::testing('a simple string');

will send us the specified warning.