- * tally -> new_hash

- * tally(hash) -> hash

- * Returns a hash containing the counts of equal elements:

- * - Each key is an element of +self+.

- * - Each value is the number elements equal to that key.

- * With no argument:

- * %w[a b c b c a c b].tally # => {"a"=>2, "b"=>3, "c"=>3}

- * With a hash argument, that hash is used for the tally (instead of a new hash),

- * and is returned;

- * this may be useful for accumulating tallies across multiple enumerables:

- *

- * hash = {}

- * hash = %w[a c d b c a].tally(hash)

- * hash # => {"a"=>2, "c"=>2, "d"=>1, "b"=>1}

- * hash = %w[b a z].tally(hash)

- * hash # => {"a"=>3, "c"=>2, "d"=>1, "b"=>2, "z"=>1}

- * hash = %w[b a m].tally(hash)

- * hash # => {"a"=>4, "c"=>2, "d"=>1, "b"=>3, "z"=>1, "m"=> 1}