What is the difference between clicking and "send mouseup"

[Victor Eijkhout]

What is the difference between clicking ona  button with a "mouseup" 
handler, and typing <send "mouseup" to button "a"> in the message 
box, the latter divided up in cases where the hand and the pointer 
tool are enabled?

Here's the behaviour that I see:
message box, pointer tool enabled: nothing happens
message box, hand tool enabled: error message
Script compile error:
Error description:
clicking on the button: it works, or sometimes rev crashes

I have no idea even where to start analysing this situation.
-- 
Victor Eijkhout <eijkhout at cs.utk.edu>
tel: 865 974 9308 (W), 865 673 6998 (H), 865 974 8296 (F)
http://www.cs.utk.edu/~eijkhout/