my $backup_dir = "/home/username/Ubuntu One";

# dump the database and gzip it
my @mysqldump = ("mysqldump","--add-drop-table","-uroot","-ppassword","mydatabase","|","gzip","-9c",">","$backup_dir/mydatabase.sql.gz");

system(@mysqldump);

##</code><code>##

mysqldump: unknown option '-9'