Redmine

why parse extension if its not using?

See regexp.
ext <- $2 <- (bmp|gif|jpg|jpe|jpeg|png)

I mean ext variable assign, but not using anywhere

["test.txt", "test.png"].each do |s|
  s.gsub(/([^\/"]+\.(bmp|gif|jpg|jpe|jpeg|png))/) do |m|
    filename, ext = $1, $2
    puts $2
  end
end

$ ruby a.rb 
png

why do you instantiate ext object if you don't use it at all?