How do you add a batch of new language keys to current language file?

I have a lot of language keys to add to the current English language file on my site.  However, the language add key feature in the admin section only allows you to add one key at a time.

How can I add a lot of language keys at once?  Can I simply mod the lang-en.php file?  (I tried that and it didn't work.)  What other files or database tables/parameters do I need to modify to bypass the admin feature?

Thanks

I would try exporting the language (look for "Export" link, next to the language name).

Edit the exported file, adding your new keys, then re-import the file.  (above and to the right of the export link, there are "List  Create  Export" choices, choose Export.