$ sudo apt-get update
$ sudo apt-get install lua-rex-onig 

lua-rex-onig is installed in your system.

Make ensure the lua-rex-onig package were installed using the commands given below,

$ sudo dpkg-query -l | grep lua-rex-onig *

You will get with lua-rex-onig package name, version, architecture and description in a table

lua-rex-onig package basic information: