In order to restore database/tables on active database. You need to use partial backups i.e. backup selected database/tables first. You need to use --include, --tables-file or --databases option to backup selected database/tables.
In order to restore partial backup couple of prerequisites you need to meet. Tables should be created with innodb_file_per_table option enabled. i.e. each table data should reside on it’s own tablespace (.ibd) file and enable innodb_expand_import or innodb_import_table_from_xtrabackup depends on percona server version for the the last option. Further, those options need to be enable where you want to import the schema/tables.
After that you need to prepare backup with --export option, then create tables manually where you need to import, discard the existing tablespace, Copy the .exp & .ibd files to the datadir and finally import the tablespace. Also, you can check this thread for help on it [url]http://www.percona.com/forums/questions-discussions/percona-xtrabackup/8315-restore-one-table-from-xtrabackup-s-full-backup[/url] and check the Xtrabackup partial backup documentation.
I recommend to test it before applying it to production and create backup of active database.