$|++;
package Foo;
{

    use strict;
    use warnings;
    use warnings::register;

    sub t {
        warnings::warnif "Bang! '@_'";
        print ": @_\n";
    }
}

package main;
{

    no warnings;
    Foo::t('no warnings');
}
{
    use warnings;
    Foo::t('use warnings');
}
{
    use warnings;
    no warnings 'Foo';
    Foo::t('no warnings "Foo"');
}
{
    no warnings;
    use warnings 'Foo';
    Foo::t('use warnings "Foo"');
}
__END__
: no warnings
Bang! 'use warnings' at C:\Temp\warnings_register.pl line 23
: use warnings
: no warnings "Foo"
Bang! 'use warnings "Foo"' at C:\Temp\warnings_register.pl line 33
: use warnings "Foo"
[download]