I intuitively knew this was the case, but wanted to do some research before posting an answer. The distinction between naming and assignment can be a little subtle. And you beat me to the punch.

But I thought this page was interesting:

http://www.haskell.org/haskellwiki/Pronunciation

'=' is pronounced as 'is'.

So you'd say something like 'main is the function that evaluates the expression...' Traditional assignment would be something more like 'the value stored in the container main now becomes the expression...'