Send only if key was pressed alone

Question

I'd like to remap my windows key to something else, but also I'd like to keep all windows key based shortcut.

In pseudo code it would be something like this:

when LWin Down until LWin Up if not LWin down abort else execute command

Answer 1

Release the left windows key within 0,3 seconds after pressing it, to do something else (e.g. to send a):

~LWin::
KeyWait, LWin
return

~LWin Up::
Send {LWin Up}
If (A_PriorHotKey = "~LWin" AND A_TimeSincePriorHotkey < 300)
    Send, a
; else  ; another action after long press (not recommendet)
    ; Send, b
return

EDIT:

Try also this:

LWin up::
If (A_PriorKey = "LWin")
    Send a
return

; In this case its necessary to define a custom combination by using "&" or "<#" 
; to avoid that LWin loses its original function as a modifier key:

<#d:: Send #d  ; <# means LWin