I did:
git clone https://github.com/tadzik/rakudobrew ~/.rakudobrew
export PATH=~/.rakudobrew/bin:$PATH
rakudobrew build moar --configure-opts=--prefix=/opt

Then trying to build panda:
(skardev)root@pinkpony:~# rakudobrew build panda --configure-opts=--prefix=/opt
Cloning into 'panda'...
remote: Counting objects: 4389, done.
remote: Total 4389 (delta 0), reused 0 (delta 0), pack-reused 4389
Receiving objects: 100% (4389/4389), 741.51 KiB | 0 bytes/s, done.
Resolving deltas: 100% (1975/1975), done.
Checking connectivity... done.
rakudobrew: perl6: command not found

but :
(skardev)root@pinkpony:~# perl6 --version
This is perl6 version 2015.10-309-g9f14995 built on MoarVM version 2015.10-92-g0181385