The input to this function is a matlab/simulink function name, such as 'rand' as a string. The function checks the version in which the input function was introduced. This function also accepts a group as input functions to check. See the following examples:
Example 1:
>> when('rand')
## rand is a built-in function (Introduced before R2006a)
Example 2:
func_name = {'rand','plot','grid','findstr','weboptions'};
when(func_name)
## rand is a built-in function (Introduced before R2006a)
## plot is a built-in function (Introduced before R2006a)
## grid is a Matlab function or an ordinary m-file (Introduced before R2006a)
## findstr is a built-in function (Introduced before R2006a)
## weboptions is a Matlab function or an ordinary m-file (Introduced in R2014b)