sort strings by interpreting them as integrals

[Andrej Mitrovic]

void main()
{
    string[] x = ["_100", "_10", "_20"];
    sort(x);
    writeln(x);
}

result:
["_10", "_100", "_20"]

I need to treat these as if they were integrals, although the
underscore complicates things here since it should be ignored. So the
result I want is:
["_10", "_20", "_100"]

How would you implement that? It could be a nice exercise! :)