Batch Create Users extras format

I am trying to put two or more names in the extras field of a Batch Create Users file and can not figure out what delimiter to use.

a single username works
Bob:Bob:itsme:0:1::webguy:::
makes bob and webguy@domain.com

but these attempts do not work.
Bob:Bob:itsme:0:1::webguy tester:::
Bob:Bob:itsme:0:1::webguy,tester:::
Bob:Bob:itsme:0:1::webguy;tester:::
Bob:Bob:itsme:0:1::webguy@domain.com tester@domain.com:::

any clue on how to get 2 or more extras ?