Regular Expressions

• Avoid using $1-9 as it can be hard to track
  what they contain. Named groups can be used instead.
  ^[link]

    # bad
    /(regexp)/ =~ string
    ...
    process $1
    # good
    /(?<meaningful_var>regexp)/ =~ string
    ...
    process meaningful_var

• Be careful with ^ and $ as they
  match start/end of line, not string endings. If you want to match the whole
  string use: \A and \z.^[link]

    string = "some injection\nusername"
    string[/^username$/]   # matches
    string[/\Ausername\z/] # don't match

• Use x modifier for complex regexps. This makes
  them more readable and you can add some useful comments. Just be careful as
  spaces are ignored.^[link]

    regexp = %r{
      start         # some text
      \s            # white space char
      (group)       # first group
      (?:alt1|alt2) # some alternation
      end
    }x