I'd missed that in the POD. However, the POD for Tk::Entry says exactly the same, word for word, but Entry allows the text to be changed programmatically no matter what the state. The key difference is between what the user is allowed to do (which is what state controls) and what the programmer is allowed to do.

Tk::ROText won't work for me, I need the text to be read/write for the user, just not all the time.