From the help file.
The fact that it works without the '=' is a 'happy accident'.
I've seen cases where it most certainly doesn't work, and has caused the scripter much grief.
In any case, we're going off topic here ;P
I am aware of the help file...
I've never had a problem with not using an equals sign. I would be interested in hearing about one of these cases where it most certainly doesn't work (perhaps in a private message if this is too off topic...)