Was actually curious so went poking and I think it's a bug / mis-implemented feature that won't work as is now (presuming I'm reading the docs right and my empirical messing around was done correctly).

According to the documentation it's so that you can (paraphrasing) define class methods which will override the defaults for things like requires_firewall (which looks like the only specific method at any rate). But since the Net::Config would be a child of the putative Net::LocalCfg class then its (Net::Config) local version would override the parent's (Net::LocalCfg) implementation.

To do what it says on the tin you'd need to have your own subclass of Net::Config with the special behavior therein so that when you call the class method on that it'd do the right thing and find your custom overridden version.

$ cat foo/Net/LocalCfg.pm
#!/usr/bin/env perl
use 5.034;
package Net::LocalCfg;

BEGIN { say qq{## Loaded my LocalCfg}; }

sub requires_firewall {
  my( $class ) = shift;

  say STDERR qq{## LocalCfg requires_firewall '$_[0]'};

  return (rand() < 0.5) ? 1 : 0;
}

1;

__END__
$ perl -I ./foo -MNet::Config -E 'say Net::Config->requires_firewall( 
+q{google.com} )'
## Loaded my LocalCfg
0
$ perl -I ./foo -MNet::Config -E 'say Net::LocalCfg->requires_firewall
+( q{google.com} )'
## Loaded my LocalCfg
## LocalCfg requires_firewall 'google.com'
0
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