Inserts value at the head of the list stored at key, only if key already exists and holds a list. In contrary to LPUSH, no operation will be performed when key does not yet exist.

@return

@integer-reply: the length of the list after the push operation.

@examples

LPUSH mylist "World"
LPUSHX mylist "Hello"
LPUSHX myotherlist "Hello"
LRANGE mylist 0 -1
LRANGE myotherlist 0 -1