The 32-year-old Pakistan bowler was cleared after visa issues threatened to rule him out of the Scorchers' tournament opener.
Arafat took 12 wickets in six Big Bash League matches last season at an economy rate of 7.37 and was regularly used to bowl at the death.
"It was a huge morale boost for the team," Langer said.
"Guys who can bowl at the death are like gold in any team. He adds great experience.
"And he can also bat. That's a bonus for us as well.
"Just to have that experience and confidence is very important for any team."
Perth have won just one match in two previous Champions League Twenty20 tournaments.
The Scorchers play the Dolphins of South Africa on Saturday.