@count(tab, value)
@count(map, value)
@count(string, value)

computes the number of times the second argument appears in the first argument. For a map, the second argument refers to a value stored in the dictionary. For a string, the second argument must be a string and the call returns the number of occurences of the first character in the first string:

       @count("abacaa", "a")

returns 4.

See also @find, @member and @occurs.