[sub_ubi]

The format is mytag=opt1|opt2|opt3

This works fine on 3.6.x

However, it's not compatible with PHP5. If you use it on a server with php5 you will get this error:

Warning: array_merge() [function.array-merge]: Argument #1 is not an array in /includes/class_bbcode.php(2341) : eval()'d code on line 7

To make it compatible with PHP5, go to your plugin manager and in,
bbcode_fetch_tags
replace

$replace = array_merge($param, explode('|', $options));

with

$replace = array_merge((array)$param, (array)explode('|', $options));

and it will work fine.