dpkg -l ¦ grep alien

Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Installed/Config-files/Unpacked/Failed-config/Half-installed
|/ Err?=(none)/Hold/Reinst-required/X=both-problems (Status,Err: uppercase=bad)
||/ Name Version Description
+++-================-================-================================================
ii grep 2.5.1.ds1-4 GNU grep, egrep and fgrep
ii alien 8.48 install non-native packages with dpkg

Use this to get alien:
apt-get update
apt-get install alien