$ sudo apt-get update
$ sudo apt-get install elpa-persp-projectile 

elpa-persp-projectile is installed in your system.

Make ensure the elpa-persp-projectile package were installed using the commands given below,

$ sudo dpkg-query -l | grep elpa-persp-projectile *

You will get with elpa-persp-projectile package name, version, architecture and description in a table

elpa-persp-projectile package basic information: