How to declare a varible in a case statement for use afterwrads

[cblake]

There are a few constructs just like that where analogy making from the 
constraints of other programming languages fail you. A similar example is 
try-except expressions. I.e., this works:
    
    
    import tables
    var t: Table[int, int]
    let x = try: t[0] except: 1
    
    
    Run