variable_if, variable_unless

{
    "description": "Pressing the a key while holding the escape key launches Activity Monitor",
    "manipulators": [
        {
            "type": "basic",
            "from": {
                "key_code": "escape",
                "modifiers": { "optional": ["any"] }
            },
            "to": [
                {
                    "set_variable": {
                        "name": "escape_pressed",
                        "value": true,
                        "key_up_value": false
                    }
                }
            ],
            "to_if_alone": [{ "key_code": "escape" }]
        },
        {
            "type": "basic",
            "from": {
                "key_code": "a",
                "modifiers": { "optional": ["any"] }
            },
            "to": [
                {
                    "software_function": {
                        "open_application": {
                            "bundle_identifier": "com.apple.ActivityMonitor"
                        }
                    }
                }
            ],
            "conditions": [
                {
                    "type": "variable_if",
                    "name": "escape_pressed",
                    "value": true
                }
            ]
        }
    ]
}

{
    "type": "variable_if",
    "name": "variable name",
    "value": variable value
}