Nothing
Code
new_pre_release_identifier(c("", "-1", "0", "00", "1", "Foo", "bar", NA))
Output
<empty>
-1 <alphanumeric>
0 <numeric>
00 <alphanumeric>
1 <numeric>
Foo <alphanumeric>
bar <alphanumeric>
<NA>
Any scripts or data that you put into this service are public.
Add the following code to your website.
For more information on customizing the embed code, read Embedding Snippets.