(Sorry for not getting to you sooner; I was on vacation.)

Your module doesn't give warnings because there's nothing to warn. Even if you added use warnings to the module, there still wouldn't be any warnings. Here's an example of -w affecting modules:

>type Foo.pm
package Foo;

sub foobar {
   print undef;
}

1;

>type foo.pl
use Foo;
Foo::foobar();

>perl -w foo.pl
Use of uninitialized value in print at Foo.pm line 4.
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