re = /oz(3[4-9]|[4-9][0-9]|[1-9][0-9]{2}|[12][0-9]{3}|3[0-8][0-9]{2}|39[0-7][0-9]|398[0-2])/
str = 'oz31 oz32 oz33 oz34 oz35 oz55 oz100 oz123 oz999 oz1000 oz2000 oz3000 oz3981 oz3982 oz3983'
# Print the match result
str.scan(re) do |match|
puts match.to_s
end
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html