A calculator using reverse polish notation, written in Ruby

reverse_polish_calc.rb

#!/usr/bin/env ruby

arr = []
$stdin.each_line do |n|
  n.chop!
  break if %w(exit quit).include?(n)
  arr << (/[[:digit:]]+/ === n ? n.to_f : n.to_sym)
  if arr.last.is_a?(Symbol)
    if arr.length < 3
      puts 'Not enough numbers in stack.'
      arr.pop
    else
      fun, op2, op1 = arr.pop, arr.pop, arr.pop
      arr << op1.send(fun, op2)
    end
  end
  puts arr
end