The function takes an input string and inserts the pattern "VY" after the second character of the input string. 

[CODE]: Here is a Python code that approximates the behavior of the function:

```python
def f(x):
    return x[:2] + "VY" + x[2:]
```

This code splits the input string after the second character, adds the pattern "VY", and concatenates the remaining part of the input string.