Rubyにおける正規表現の使用に関する分析

  match = string[/regexp/] # get content of matched regexp
  first_group = string[/text (grp)/, 1] # get content of captured group
  string[/text (grp)/, 1] = 'replace' # string => 'text replace'

  /(first|second)/ # bad
  /(? :first|second)/ # good

  /(regexp)/ =~ string
  ...

  # bad
  process $1

  # good
  process Regexp.last_match[1]

  # bad
  /(regexp)/ =~ string
  ...
  process Regexp.last_match[1]

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

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

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