Count occurrences of a substring

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Create a function, or show a built-in function, to count the number of non-overlapping occurrences of a substring inside a string.

The function should take two arguments:

• the first argument being the string to search, and
• the second a substring to be searched for.

It should return an integer count.

The matching should yield the highest number of non-overlapping matches.

In general, this essentially means matching from left-to-right or right-to-left.