stand_back_everyone_i_know_regular_expressions.rb

delimiter            = "[-/.]+"
  
century_prefix       = "(?:19|20)"
under_ten            = "(?:0[1-9]+)"
ten_to_twelve        = "(?:1[012]+)"
ten_and_under_thirty = "(?:[12]+[0-9]+)"
thirties             = "(?:3[01]+)"

pattern = %r[
  (
    #{century_prefix}[0-9]{2}     # year e.g. 1901, 2036
  )

  #{delimiter}

  ( 
    #{under_ten}
    |
    #{ten_to_twelve}
  )
  
  #{delimiter}
  
  (
    #{under_ten}                  # e.g. 01, 09
    |
    #{ten_and_under_thirty}       # e.g. etc
    |
    #{thirties}
  )

]x # <- the magickal x; extended mode - whitespace is ignored. Instead, use \s to match whitespace.

if "2010-02-17"[pattern]
  year, month, day = $1, $2, $3
  # Insert multi-million dollar idea here
end