$ sudo apt-get update
$ sudo apt-get install libsys-hostname-long-perl 

libsys-hostname-long-perl is installed in your system.

Make ensure the libsys-hostname-long-perl package were installed using the commands given below,

$ sudo dpkg-query -l | grep libsys-hostname-long-perl *

You will get with libsys-hostname-long-perl package name, version, architecture and description in a table

libsys-hostname-long-perl package basic information: