Issues with alt+left

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First, let me express my thankfulness to the Hammerspoon developers for creating such a useful and well-designed piece of software. Currently, I'm trying to use Hammerspoon to write some custom shortcuts on my Macbook. Specifically, I want the cmd+left shortcut (which traditionally moves the cursor to the beginning of the line) to have the behavior of the alt+left shortcut (which traditionally moves the cursor one "word" backwards). I tried putting this in my init.lua:

hs.loadSpoon("ReloadConfiguration")
spoon.ReloadConfiguration:start()

hs.hotkey.bind({"cmd"}, "Left", function()
  hs.eventtap.keyStroke({"alt"}, 'Left')
end)

And it compiles successfully and stops the cmd+left shortcut from moving the cursor to the beginning of the line, but it seems like the alt+left keystroke does not always get emitted, triggering only about 40-60% of the time. This means most of the time pressing cmd+left does nothing. Any ideas on how to fix this?