You create a file, e.g. /home/user/bl.sh with the code as content, then run then you can call the script by running /home/user/bl.sh

It toggles blacklight mode on or off. Note that, as MohammadAG stated, stop switch doesn't work while backlight is off.

Also, it will effectively turn the screen into monochrome mode, which has kind of a retro vibe to it