proc Expand(Range);
char Range;
int  Lo, Hi, N;
[Text(8, Range);
loop    [Lo:= IntIn(8);
        BackUp;         \get what terminated number
        case ChIn(8) of
          ^-:   [Hi:= IntIn(8);
                for N:= Lo to Hi do
                    [IntOut(0, N);
                    if N < Hi then Text(0, ", ");
                    ];
                BackUp;
                if ChIn(8) = $1A \EOF\ then quit;
                ];
          ^,:   IntOut(0, Lo)
        other \EOF\ [IntOut(0, Lo);  quit];
        Text(0, ", ");
        ];
];

Expand("-6,-3--1,3-5,7-11,14,15,17-20")