08. Metacharacters - The Character Class

• By using character classes, we can already start to write some regular expressions that are more interesting and more powerful than we could when we only knew about literal characters.
• For example, let's extend the regular expression that we had before:

    [ea]
          

  by adding some more detail:

    gr[ea]y
          

• We now have a very useful regex, that can match either the word "grey" or the word "gray"!
• This would be ideal for finding words that someone may have spelt differently throughout a document.