I have a data file that contains a single region and then a varying number of cities/towns as follows;-

```
South,London,Guildford,Winchester
North,Manchester,Leeds
East,Norwich

```

I need to produce an output like this using AWK

```
South,London
South,Guildford,
South,Winchester
North,Manchester etc

```

It must loop through only when there is a city/town present.