R: How to make a for loop for each vector in list : I have a list l, contains four vectors, each vector contains a number of elements, the vectors are not the same length. 

    l<- list(2:4,3:5,4:7,5:7)

      for ( i in length(l)){

         print(l)
       }

    [[1]]
    [1] 2 3 4
    
    [[2]]
    [1] 3 4 5
    
    [[3]]
    [1] 4 5 6 7
    
    [[4]]
    [1] 5 6 7

I would like to add value 2 to all the elements of each vector in the list using for loop.  
Maybe we need (**two for loops**) The external  will be for the list and the internal will be for each vector of the list, I would like to obtain  the following result :

      
        [[1]]
        [1] 4 5 6
        
        [[2]]
        [1] 5 6 7
        
        [[3]]
        [1] 6 7 8 9
        
        [[4]]
        [1] 7 8 9


**Please note that:** the original list contains 389 vectors, each vector contains not less than  45 elements. 
