Example-001: String Length

   puts 'That is an object'.size   # => prints 17

Example-002: Reversing

   puts 'This is not a palindrome'.reverse   # => prints 'emordnilap a ton si sihT'

Example-003: Single substitution

   puts 'a banana'.sub('a', '*')   # => prints '* banana'

Example-004: Global substitution

   puts 'a banana'.gsub('a', '*')   # => prints '* b*n*n*'