thufir@arrakis:~/java$ 
thufir@arrakis:~/java$ ruby java.rb 
clean...
working directory:              /home/thufir/java

./tasks.rb:7:in `clean': undefined method `remove_dir' for Tasks:Module (NoMethodError)
        from java.rb:5
thufir@arrakis:~/java$ 
thufir@arrakis:~/java$ cat tasks.rb 
module Tasks

        def Tasks.clean
                puts "clean...\n"
                Dir.chdir("/home/thufir/java/")
                puts "working directory:\t\t" + Dir.getwd + "\n\n"
                remove_dir("/home/thufir/java/build/")
        end

        def Tasks.compile
                puts "compile...\n\n"
                Dir.chdir("/home/thufir/java/src/")
                puts "working directory:\t\t" + Dir.getwd + "\n\n"
                system("javac -cp . -d /home/thufir/java/build/ com/web_tomorrow/CPTest2.java ")
        end


        def Tasks.package
                puts "package...\n\n"
                Dir.chdir("/home/thufir/java/build/")
                system("java com.web_tomorrow.CPTest2")
                system("jar -cf foo.jar /home/thufir/java/build/com/web_tomorrow/*.class")
        end

end

thufir@arrakis:~/java$