J how to escape "," symbols?

Hey, I am trying to pass a string with `,` symbols in it, tried several ways, but didn't succeded to escape it..
```
❯ j foo :~ "http://example.com/a,b,c,d", bar: baz
{
"bar": "baz",
"foo": [
"http://example.com/a",
"b",
"c",
"d"
]
}
```

`foo` should be a string in my case, not an array...