Topic on Extension talk:Arrays

As the topic says.

Unfortunately there isn't. Per ExtArrays.php line 188, the only valid values for the print option are list, which prints the input as a simple list, and pretty, which instead pretty prints it with the last two items separated by and (or presumably the interface language equivalent, depending on what exactly the $wgLang->listToText() function does).

If your wiki has Extension:Page Forms installed, you can instead use #arraymap, which allows you to change the delimiter used between the final two items in the array.