brewkit.rb changes ENV destructively, so lets not do that everytime a formula
is required. Now it's possible for other tools to require a formula
description without worrying about side-effects.
mmv is a program to move/copy/append/link multiple files according to a set of
wildcard patterns. This multiple action is performed safely, i.e. without any
unexpected deletion of files due to collisions of target names with existing
filenames or with other target names.