class Rake::FileList

FileList['a.c', 'b.c'].sub(/\.c$/, '.o') => ['a.o', 'b.o']
Example:

element of the original list.
Return a new FileList with the results of running +sub+ against each

def sub(pat, rep)
  inject(FileList.new) { |res, fn| res << fn.sub(pat,rep) }
end