I did a bit of hacking with warnings.pm. What's throwing the module off is its use of the caller function.

Here is an illustration:

package MyAbc;

warnings::register;

sub foo
{
  warnings::warn "foo", if (warnings::enabled);
  bar;
}

sub bar
{
  warnings::warn "bar", if (warnings::enabled);
}

Warnings will work in foo because it is "top-level", but they do not work in bar because it's a function within a function.

That is, they don't work if I use warnings 'MyAbc', but they will work if I run Perl with the -w switch.

Correction ... if I run foo from a calling module, we don't see the warning from foo but we do see it from bar. However, when we run bar directly we don't see it.

Even stranger, a module that I'm working on has the opposite effect of my correction. This is strange indeed.