irb(main):003:0> message = "hello" => "hello" irb(main):004:0> message.upcase => "HELLO" irb(main):005:0> puts message hello => nil irb(main):006:0> message.upcase! => "HELLO" irb(main):007:0> puts message HELLO => nil irb(main):008:0> message.downcase! => "hello" irb(main):013:0> greetings = " hello world! " => " hello world! " irb(main):014:0> puts greetings hello world! => nil irb(main):015:0> greetings.strip!.capitalize! # here we are chaining methods. => "Hello world!" irb(main):016:0> puts greetings Hello world! => nil irb(main):017:0> irb(main):061:0* htmlgreeting = "[html][body][strong]hello world[/strong][/body][/html]" => "[html][body][strong]hello world[/strong][/body][/html]" irb(main):062:0> puts htmlgreeting [html][body][strong]hello world[/strong][/body][/html] => nil irb(main):063:0> puts htmlgreeting.gsub("[","<").gsub("]",">") hello world => nil irb(main):064:0> irb(main):064:0> weekdays = "monday->tuesday->wednesday->thursday->friday" => "monday->tuesday->wednesday->thursday->friday" irb(main):065:0> array_weekdays = weekdays.split("->") => ["monday", "tuesday", "wednesday", "thursday", "friday"] irb(main):066:0> puts array_weekdays[2] wednesday => nil irb(main):067:0>