$ sudo apt-get update
$ sudo apt-get install libkde4-ruby 

libkde4-ruby is installed in your system.

Make ensure the libkde4-ruby package were installed using the commands given below,

$ sudo dpkg-query -l | grep libkde4-ruby *

You will get with libkde4-ruby package name, version, architecture and description in a table

libkde4-ruby package basic information: