[Typo3] [loginUser = *] test for BE users?

[Matthew Manderson]

This is crazy, must be something so simple. There is just no reason I can see 
why this setup TS does not work.

[globalVar = TSFE : beUserLogin < 0]
temp.mainTemplate.subparts.edit = HTML
temp.mainTemplate.subparts.edit.value = You are logged in?
[else]
temp.mainTemplate.subparts.edit = HTML
temp.mainTemplate.subparts.edit.value = You are not logged in?
[global]

I can safely change the condition to test for say browser type and it works 
but beUserLogin does not work.

I tested for 'null' and it seems to match. Is it possible my installation does 
not have the default '0' set.

Any ideas how I can check this.
Thanks, 
Matthew