Installing a language with Amazon RDS?

I am using an instance of Postgres on RDS and I am trying to run: => create language plperlu; but I get: ERROR: must be superuser to create procedural language "plperlu" If I run: => grant rds_superuser to treex; NOTICE: role "treex" is already a member of role "rds_superuser" GRANT ROLE Is it actually possible to use perl extensions for Postgres on RDS or the only solution is creating a Docker instance with Postgres and Perl modules preinstalled?