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>