# File lib/rake/alt_system.rb, line 71
71:     def find_runnable(file)
72:       if file =~ RUNNABLE_PATTERN
73:         file
74:       else
75:         RUNNABLE_EXTS.each { |ext|
76:           if File.exist?(test = "#{file}.#{ext}")
77:             return test
78:           end
79:         }
80:         nil
81:       end
82:     end