srt.rb

                        require 'time'                            
                      require 'optparse'                          
                                                                  
                                                                  
                     %w[operation time].                          
                inject(OptionParser.new){|o,i|                    
      o.on("-"+c=i[0,1],"--#{i} X"){|v|eval("$#{c}=v")}           
      o}.parse!;$t,$o=$t.tr(',','.').to_f,$o=='sub'?:-:           
     :+;puts File.read(ARGV[0]).gsub(/^(.*) --> (.*)$/){          
     [$1,$2].map{|x|(t=Time.parse(x.strip).send($o,$t)).          
       strftime("%H:%M:%S,#{t.usec}00")[0,12]}*' --> '}