gistify751650.dice.rb

    def parse(dices)
      %r{^
          (?<top_or_bottom>t|b)? # Flag for finding the top or bottom dice
          (?<tb_number>\d)?      # Number of top or bottom dice
          \[(?<dice>.*)\]        # The main dice string, to be parsed later
          (?<explode>\*)?        # Reroll (explode) die rolls? (i.e. 6 on 1d6)
          (?<plus>(\+|\-)\d+)?   # Additional points to add to roll (or subtract)
          \=?                    # = Target Number or range follows...
          (?<target>.*)?$        # The target number (single 4, range 4..6, above 4+, below 4-)
        }x =~ dices
      die_set = eval "[" + string_to_dice_array(dice) + "]"
      dice_pool({set: die_set, top: tb_number.to_i, plus: plus.to_i})
    end

That is one readable regex.