string.find does act differently based on input?

[meino.cramer@...]

Hi,

I did this interactively after I had the same behaviour
in my script.

    Lua 5.1.4  Copyright (C) 1994-2008 Lua.org, PUC-Rio
    > a="find(test)"
    > =string.find(a,"test")
    6	9
    > =string.find(a,"(" )
    stdin:1: unfinished capture
    stack traceback:
        [C]: in function 'find'
        stdin:1: in main chunk
        [C]: ?
> 

Why does string.find find the word "test" but not the "(" ?

Best regards,
mcc