Running npm `postinstall` script after the original `npm install` finishes? (Maybe by using a Node trick?)

I'm trying to create an npm module that has a postinstall script that will modify the user's package.json and re-install packages. I'm almost there, but the problem I'm having is that the npm CLI runs my postinstall script too early.

Is there a way, maybe by using Node or system level trick, to wait for the whole npm install process to exit before my script runs? Like when npm calls my postinstall script, at that time I can register another script to run after npm install finishes?

via M.K. Safi