How to run a shell command but not waiting for the result ?

[LI NGOK LAM]

I've tried to use exec, system, and ``. And also with and without $| = 1;
but seems unable to do what I want.

What I want to do is suppose like this :

print "Start";
exec "notepad";
print "End";

but I found my results are :

If I can see "End", the notepad won't come,
If I can run the notepad, I can't see the End
until I close the notepad.

So what can I do to make it possible to run the notepad, 
but then just leave it alone and go on with the rest of the
code ?

TIA