使用额外的软件包编译Go技巧

I'd like to try out the exp/regexp package. Currently Go tip's ./all.bash command compiles including only exp/regexp/syntax. I've been looking around the makefiles and I see it builds a Make.deps but couldn't figure out how it selects the packages that are included. What should I change to build Go with exp/regexp?

Duh, it was right in front of my eyes! Add the package dir to src/pkg/Makefile:

DIRS=\
    archive/tar\
    archive/zip\
    asn1\
    ...
    exp/regexp\
    ...