{    
    max = { % number a, number b, number c -> number or "error"
        [ c = "" : c = "0"; ] % by default use "0" if c not specified
        ab = {} + ("test " + a + " -le " + b).syscall;
        [ ab = "1" :
            ac = {} + ("test " + a + " -le " + c).syscall;
            [ ac = "1" : ^c; ]
            [ ac = "0" : ^a; ]
        ][ ab = "0" :
            ^ { a = *a; b = *c; c = *b; } + *max;
        ]
        ^ "error";
    }
    result = { a = "12"; b = "27"; c = "18"; } + max;
    {} + ("echo " + result).syscall;
    {} + ("echo " + ({ a = "-12"; b = "-27"; } + max)).syscall;
}