Returns a non-zero number if the specified label exists in the script.
Boolean := IsLabel(LabelName)
The name of a subroutine, hotkey, or hotstring. The trailing colon(s) should not be included.
This function returns 1 (true) if LabelName exists in the script, otherwise 0 (false).
This function is useful to avoid runtime errors when specifying a dynamic label in commands such as Gosub, Hotkey, Menu, and Gui.
Reports "Subroutine exists" because the subroutine does exist.
if IsLabel("Label") MsgBox, Subroutine exists else MsgBox, Subroutine doesn't exist Label: return