The function takes a string input and inserts the character '3' after first half of the input length. Then, it appends the character 'l' to the end of the transformed string.

[CODE]: 

```python
def fx(s):
    n = len(s)
    first_half = s[:n//2]
    second_half = s[n//2:]
    transformed = first_half + '3' + second_half + 'l'
    return transformed
```

Let me know if you need more testing or information.