re = /(?<=((birds?)|(pigs?)).*)\b[a-z]{3,}\b(?=.*((birds?)|(pigs?)))/mi
str = 'Pigs are farm animals. Birds are not
My bird fly in his cage. My pig run in the garden.'
# 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