Refactor long if elsif statement

I have a page where you can copy the contents of an excel spreadsheet and put it into a text box and press import.
It then goes through the text and matches a line to find out what customer the import is for.

the if elsif statement looks like this.

if lines.first.match(/certain text/)
  do stuff
elsif lines.first.match(/certain text/)
 do stuff
elsif
  ...
end

and it is now extremely long is there a way to make this better?

I’d suggest you to use the case expression, so you can do something like this:

case site
when "stackoverflow.com"
  "Ask basic questions such as aforementioned"
when "forum.upcase.com"
  "Discuss controversial topics and contribute to the community"
end

case expression is designed for long chains of obviously cases, and helps you to maintain readability of your code, while basically it is the same thing as if.