Just use `lists:sublist/2` here.

```erlang
7> lists:sublist([], 3).
[]
8> lists:sublist([a,b], 3).  
[a,b]
9> lists:sublist([a,b,c], 3).
[a,b,c]
10> lists:sublist([a,b,c,d,e], 3).
[a,b,c]
```