Finding if a value exists in a cell containing comma separated text

I have a column which contains a comma-separated list of numbers:"3, 5, 11"

I need like to have a continuous bunch of cells, each with the value true or false based on whether the corresponding cell value exists in the CSV string.IE cell 1 would check for "1" in the string, cell 2 for "2" in the string etc.

SEARCH() isn't a good solution, because searching for "1" would yield true even if only the value 11 exists (and not 1).

So in a sense, it's about doing a SPLIT, then searching the result of that function.

What would be the formula for that in one of those cells?