Install a gem automatically if it's not installed

I have faced a problem of Gem::LoadError while using same .irbrc with different rubies. Especially when a new ruby version is installed. If i require some gems in .irbrc, i get the error 'cannot load such file --'. To counter this, if a gem is not present, there should be a way to install it and reload the path.
Following snippet of code does just that.

# Check for presence of required gems. 
# If not present, install the gems
["wirble", "awesome_print"].each do |gem|

  begin
    gem "#{gem}"
  rescue Gem::LoadError
    `gem install #{gem}`
     Gem.clear_paths
  end

end

Now after this code you can safely require wirble or awesome_print, without worrying whether it is installed on your system or not.