karabiner/left_ctrl2caps_lock.json

{
    "description": "korean <-> english by left ctrl",
    "manipulators": [
        {
            "from": {
                "key_code": "left_control",
                "modifiers": { "optional": ["any"] }
            },
            "to": [
                {
                    "key_code": "left_control",
                    "lazy": true
                }
            ],
            "to_if_alone": [
                {
                    "key_code": "caps_lock",
                    "hold_down_milliseconds": 100
                }
            ],
            "type": "basic"
        }
    ]
}