use VCL::Module::OS::Windows::Version_6::Vista;

my $xp = VCL::Module::OS::Windows::Version_5::XP->new();

my $vista = VCL::Module::OS::Windows::Version_6::Vista->new();

$xp->configure_firewall();

$vista->configure_firewall();

$vista->disable_aero_theme();

$xp->disable_aero_theme(); # <-- generates subroutine not defined error

$xp->reboot();

$vista->reboot();