"auto alt + yen" watcher #hammerspoon

init.lua

-- based on: http://qiita.com/tanakahisateru/items/d8a67ad89c07baf8c0da

local VK_JIS_YEN = 0x5d

watcher = hs.eventtap.new({
    hs.eventtap.event.types.keyDown
}, function(event)
    local code = event:getKeyCode()
    -- hs.logger.new('test', 'debug').d(code)
    
    if code == VK_JIS_YEN then
        local flag = event:getFlags()
        flag['alt'] = not flag['alt'] -- "reverse" alt flag
        event:setFlags(flag)
    end
end)

watcher:start()