Find all unique instance variable declarations in a Ruby Module

variable_parser.rb

seen_variables = [] 
File.open(ARGV[0], 'r').each do |line|
   line = line.strip!
   /^@\w+/.match(line) do |v|
     puts v unless seen_variables.include?(v.to_s)
     seen_variables << v.to_s
   end
 end