def check_private_network(ip)
  priv_re = /^(192\.168\.|10\.|172.16)/
  ret = false
  puts "Checking #{ip}"
  result = (ip =~ priv_re)
  if result
    ret = true
  end
  return ret
end

ip_re = "((?:[0-9]{1,3}\.){3}(?:[0-9]{1,3}))"
fun_re = Regexp.new("(#{ip_re})(?{ check_private_network($g[0])})");

# this set matches correctly, identifies i0 and i2 as private
ips = ["192.168.0.1", "1.2.3.4", "10.8.3.44", "73.55.244.2"]
# output is:
#  Checking 192.168.0.1
#  192.168.0.1 is a private net
#  Checking 1.2.3.4.0.1
#  Checking 10.8.3.44
#  10.8.3.44 is a private net
#  Checking 73.55.244.2
#  Checking 73.55.244
#
# No, I'm not sure why the 2nd check is '1.2.3.4.0.1'. A bug on my part likely.
# No, I'm not sure why the last check is not a valid IP.

# This one should identify 192.168.0.1 as a private ip
# but maybe oniguruma's optimizations break backtracking?
#ips = ["foo bar 1.2.3.4 192.168.0.1 1.2.3.4"]
# output is 
#  Checking 1.2.3.4
#
# It should 'fail' on 1.2.3.4 and move on to the 192.168 address. 
# The expected output would be:
#  Checking 1.2.3.4
#  Checking 192.168.0.1
#  192.168.0.1 is a private net
# And $1 should be 192.168.0.1, but it isn't. Bugs for me!

ips.each { |x|
  y = fun_re.match(x)
  if y.to_s.length > 0 
    puts "#{y} is a private net"
  end
}

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