BEGIN {
    my $debug = 0;
    unless ($debug) {
        $INC {"warnings.pm"} = 1;
        no strict 'refs';
        *{"warnings::import"} = sub {1;};
    }
}

use warnings;

##</code><code>##

BEGIN {
    $::DEBUG = 1;
}
use warnings $::DEBUG ? "all" : "io";  # Or some other category.