Error msg that doesn't compute

[Joe Lewis Wilkins]

Anyone know why this simple handler in 3.0 returns the error msg it  
does?

TIA, Joe Wilkins

on mouseDown
    global gMyX, gMyY
    put the mouseX into gMyX
    put the mouseY into gMyY
end mouseDown

stack "Drafting": compilation error at line 3 (Expression: bad  
factor), char 8