{
    error = "0";
    fact = { % number num -> number; set error if something is wrong
        continue = {} + ("test 1 -ge " + num).syscall;
        [ continue = "0" :
            [ {} + ("test 0 = " + num).syscall # "0" :
            *error = "1";
            ]
            ^ "1";
        ]
        nextnum = { in = *num + "-1"; } + "bc -lq".iosyscall;
        [ nextnum.result = "0" :
            result = { in = { num = **nextnum.out; } + **fact + "*" + *nextnum.out; } + "bc -lq".iosyscall;
            [ result.result = "0" :
                ^ result.out;
            ]
        ]
        *error = "2";
        ^ "0";
    }
    value = { num = "5"; } + fact;
    [ error = "0" : { in = "result: " + *value; } + "echo".iosyscall; ]
    [ error # "0" : { in = "error #" + *error; } + "echo".iosyscall; ]
}