External USB3 disk and a logical folder structure. I have at least two builds per released perl version: one threaded with using longdouble and one unthreaded. Both are 64bitall. I am also trying to revive some of my 32bit builds. Then I have several builds compiled with clan + address sanitizer, which are good to have available when doing XS stuff.
Apart from that I have quite a bunch of perl builds on HP-UX and some on AIX.
I do not use PerlBrew. I use Devel::PatchPerl and some manual insteraction on some points
Enjoy, Have FUN! H.Merijn