You're missing a backslash.
So it will look like this:
location ~* ^.+\.(jpg|jpeg|gif|css|png|js|ico|srt|txt|swf)$ {access_log off;expires 30d;}
So it will look like this:
location ~* ^.+\.(jpg|jpeg|gif|css|png|js|ico|srt|txt|swf)$ {access_log off;expires 30d;}