So I worked this out for something at work, but I'm concerned it isn't readable. What do you think?

FileParser.rb

require 'set'

class FileParser

	def initialize filename
		@set = IO.readlines(filename).collect{ |s| s.split(',').map!{ |t| t.strip } }.flatten.to_set
	end

	def match? value
		@set.include? value
	end

end

So I ended up with this, after your comments;

def initialize csv_filename
    lines = IO.readlines(csv_filename)
    lines.collect!{ |s| s.split(',') }
    lines.flatten!
    lines.map!{ |t| t.strip }
    @set = lines.to_set
end