re = /(?<=[^\/])\/(?=[^\/])([\w\s\S]*)$/
str = 'https://documentosavanzopr.s3.amazonaws.com/1090525908/3/Requests/13645/paymentSupport-a3a27d291f20b743.pdf'
# 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