karabiner.json

{
  "title": "Change caps_lock key (rev 4)",
  "rules": [{
    "description": "Change caps_lock to control if pressed with other keys, to tab if pressed alone.",
    "manipulators": [{
      "type": "basic",
      "from": {
        "key_code": "caps_lock",
        "modifiers": {
          "optional": ["any"]
        }
      },
      "to": [{
        "key_code": "left_control"
      }],
      "to_if_alone": [{
        "key_code": "escape"
      }]
    }]
  }]
}