I'm adding a second site; why not just use a handful of simple Perl scripts to convert my existing configs?

You could write a couple of small Perl scripts to do a one-time conversion job for one platform (your firewall, for instance). But then what? How do you continue to keep those configurations consistent between the two sites, as both grow and evolve? How do you keep things consistent between the firewalls and the load balancers (and the monitoring systems and the VLAN switches and the VPN concentrators and ...)? If you're doing it by hand, as most organizations currently do, you're working harder than you have to and inconsistencies are guaranteed to creep in, because people make mistakes. They make typos, they get interrupted, they get distracted, or whatever. If you're maintaining a bunch of related-but-independent configurations by hand, they're going to devolve over time.

If you use Netomata's tools to generate all of your configs, you can then easily generate revised configs whenever you need to as the sites grow and evolve.