Ah. glr is 1) a very recent in-development branch that 2) only includes the compiler so 3) panda (the module installer) isn't included and 4) it may not work even if you download and manually install a copy of it.

You might want to visit the freenode IRC channel #perl6 to straighten things out.[1] In the meantime I'm going to install the glr branch and see what I find. It might be a few hours (at most a day I think) before I can get back to you.

[1] https://kiwiirc.com/client/irc.freenode.net/#perl6

If you type rakudobrew by itself, the usage shows it is capable of a "rakudobrew build-panda" which is probably a good place to start. Panda is the Perl 6 package manager, in case that wasn't clear.