In other words, you want to test a specific subset of your application, where "specific" means "the stuff someone else doesn't support testing".

The honest way to do this is have your JS have a ishttpunit flag, similar to the isIE and isNS flags, that will remove all stuff that httpunit doesn't support.

Frankly, I think you're going about this the wrong way. On the server, you test the server. So, verify that the JS being generated is correct. Verify that the various Perl components are doing the right thing, both in isolation and together.

Then, on your target client machines, run the brower(s) you expect to support through some scripted interface and test that.

You cannot test client interactions on the server. Not even a little. You need a client to test client interactions.