Modrewrite allow numbers, letters, underscore

Question

I want to have a url that will allow for a tag to have underscores, numbers, and letters of any combination (uppercase or lowercase).

Example: tags/WhaTever_eyE_D3sire

RewriteRule ^tags/([A-Za-z0-9]+)$ tags/$1/ [R,QSA]
RewriteRule ^tags/([A-Za-z0-9]+)/$ index.php?state=tags&tag=$1 [L,QSA]

That is what I have right now. Can someone please tell me the proper syntax I need to make this happen? Thanks!