[Karabiner] FN to CTRL-L

private.xml

<?xml version="1.0"?>
<root>
    <devicevendordef>
        <vendorname>Apple_Internal_Keyboard_Vendor</vendorname>
        <vendorid>0x05ac</vendorid>
    </devicevendordef>

    <deviceproductdef>
        <productname>Apple_Internal_Keyboard_Product</productname>
        <productid>0x0273</productid>
    </deviceproductdef>

    <item>
        <name>Change FN to CONTROL_L Key</name>
        <appendix>(Change FN to CONTROL_L key in internal keyboard.)</appendix>
        <identifier>private.fn_hack</identifier>
        <block>
            <!-- change fn key to CONTROL_L key -->
            <device_only>
                DeviceVendor::Apple_Internal_Keyboard_Vendor,
                DeviceProduct::Apple_Internal_Keyboard_Product
            </device_only>
            <autogen>__KeyToKey__ KeyCode::FN, KeyCode::CONTROL_L</autogen>
        </block>
    </item>
    <item>
        <name>Change CONTROL_L to FN Key</name>
        <appendix>(Change CONTROL_L to FN key in internal keyboard.)</appendix>
        <identifier>private.control_l_hack</identifier>
        <block>
            <!-- change ctrl key to fn key -->
            <device_only>
                DeviceVendor::Apple_Internal_Keyboard_Vendor,
                DeviceProduct::Apple_Internal_Keyboard_Product
            </device_only>
            <autogen>__KeyToKey__ KeyCode::CONTROL_L, KeyCode::FN</autogen>
        </block>
    </item>
    <item>
        <name>Fn+Functional Keys to F1..F12</name>
        <appendix>(Use these settings if you activated "XXX to Fn")</appendix>
        <block>
            <device_only>
                DeviceVendor::Apple_Internal_Keyboard_Vendor,
                DeviceProduct::Apple_Internal_Keyboard_Product
            </device_only>
        </block>
        <item>
            <name>Fn+Brightness Adjust to F1,F2</name>
            <appendix>* Fn+Brightness Down to F1</appendix>
            <appendix>* Fn+Brightness Up to F2</appendix>
            <identifier>private.fn_consumer_to_fkeys_f1</identifier>
            <!-- F1 -->
            <autogen>__KeyToKey__ ConsumerKeyCode::BRIGHTNESS_DOWN, ModifierFlag::FN, KeyCode::F1</autogen>
            <autogen>__KeyToKey__ KeyCode::BRIGHTNESS_DOWN,         ModifierFlag::FN, KeyCode::F1</autogen>
            <!-- F2 -->
            <autogen>__KeyToKey__ ConsumerKeyCode::BRIGHTNESS_UP,   ModifierFlag::FN, KeyCode::F2</autogen>
            <autogen>__KeyToKey__ KeyCode::BRIGHTNESS_UP,           ModifierFlag::FN, KeyCode::F2</autogen>
        </item>
        <item>
            <name>Fn+Mission Control/Launchpad to F3,F4</name>
            <appendix>(And Fn+Expose and Fn+Dashboard to F3,F4)</appendix>
            <identifier>private.fn_consumer_to_fkeys_f3</identifier>
            <!-- F3 - F12 -->
            <autogen>__KeyToKey__ KeyCode::EXPOSE_ALL, ModifierFlag::FN, KeyCode::F3</autogen>
            <autogen>__KeyToKey__ KeyCode::DASHBOARD,  ModifierFlag::FN, KeyCode::F4</autogen>
            <autogen>__KeyToKey__ KeyCode::LAUNCHPAD,  ModifierFlag::FN, KeyCode::F4</autogen>
        </item>
        <item>
            <name>Fn+Keyboard Backlit Adjust to F5,F6</name>
            <appendix>* Fn+Keyboard Backlit Low to F5</appendix>
            <appendix>* Fn+Keyboard Backlit High to F6</appendix>
            <identifier>private.fn_consumer_to_fkeys_f5</identifier>
            <autogen>__KeyToKey__ ConsumerKeyCode::KEYBOARDLIGHT_LOW,  ModifierFlag::FN, KeyCode::F5</autogen>
            <autogen>__KeyToKey__ ConsumerKeyCode::KEYBOARDLIGHT_HIGH, ModifierFlag::FN, KeyCode::F6</autogen>
        </item>
        <item>
            <name>Fn+Music Controls to F7,F8,F9</name>
            <appendix>* Fn+Music Prev to F7</appendix>
            <appendix>* Fn+Music Play/Pause to F8</appendix>
            <appendix>* Fn+Music Next to F9</appendix>
            <identifier>private.fn_consumer_to_fkeys_f7</identifier>
            <autogen>__KeyToKey__ ConsumerKeyCode::MUSIC_PREV, ModifierFlag::FN, KeyCode::F7</autogen>
            <autogen>__KeyToKey__ ConsumerKeyCode::MUSIC_PLAY, ModifierFlag::FN, KeyCode::F8</autogen>
            <autogen>__KeyToKey__ ConsumerKeyCode::MUSIC_NEXT, ModifierFlag::FN, KeyCode::F9</autogen>
        </item>
        <item>
            <name>Fn+Speaker Controls to F10,F11,F12</name>
            <appendix>* Fn+Volume Mute to F10</appendix>
            <appendix>* Fn+Volume Down to F11</appendix>
            <appendix>* Fn+Volume Up to F12</appendix>
            <identifier>private.fn_consumer_to_fkeys_f10</identifier>
            <autogen>__KeyToKey__ ConsumerKeyCode::VOLUME_MUTE, ModifierFlag::FN, KeyCode::F10</autogen>
            <autogen>__KeyToKey__ ConsumerKeyCode::VOLUME_DOWN, ModifierFlag::FN, KeyCode::F11</autogen>
            <autogen>__KeyToKey__ ConsumerKeyCode::VOLUME_UP,   ModifierFlag::FN, KeyCode::F12</autogen>
        </item>
    </item>
</root>