Simple StringScanner solution for parsing nested braces

stack.rb

require 'strscan'

s = StringScanner.new("1{2{3}; 1{2} }")

stack = [[]]

until s.eos?
  if s.scan(/\{/)
    stack << []
  elsif s.scan(/\}/)
    tmp = stack.pop
    stack.last << tmp
  elsif s.scan(/[[:word:]]+/)
    stack.last << s.matched
  elsif s.scan(/[;\s]+/)
  end

  p stack
end