I have two columns in a large file, say

```
pro1 lig1
pro2 lig2
pro3 lig3
pro4 lig1
.....

```

Second is column redundant. I want new random combinations of double size which should not match given combination, for example

```
pro1 lig2
pro1 lig4
pro2 lig1
pro2 lig3
pro3 lig4
pro3 lig2
pro4 lig2
pro4 lig3
.....

```

Thanks.