Sure you can!

Just add the CREATE privilege:

GRANT CREATE ON `foobar%`.* TO 'foobaruser'@'%' IDENTIFY BY 'foobarpass';

And just test it:

foobaruser$ mysql
mysql> create database `foobar_one`;
Query OK, 1 row affected (0.00 sec)

mysql> create database `barfoo_one`;
ERROR 1044 (42000): Access denied for user 'foobaruser'@'localhost' to database 'barfoo_one'

Be aware that you need to escape the _ (underscore), as it acts like one character in the pattern. So «`foobar_`» will match foobar1 or foobarZ.

Yes. Just add the CREATE privilege:

GRANT CREATE ON `foobar%`.* TO 'foobaruser'@'%' IDENTIFIED BY 'foobarpass';

And just test it:

foobaruser$ mysql
mysql> create database `foobar_one`;
Query OK, 1 row affected (0.00 sec)

mysql> create database `barfoo_one`;
ERROR 1044 (42000): Access denied for user 'foobaruser'@'localhost' to database 'barfoo_one'

Be aware that you need to escape the _ (underscore), as it acts like one character in the pattern. So «`foobar_`» will match foobar1 or foobarZ.