Incorrect handling of a few specific regular expressions

When you do something like

```
!!js/regexp /efe/g/g
```

This is an invalid JavaScript RegExp literal, however it gets parsed like the following:

```
new RegExp('/efe/g', 'g');
```

Should this not be treated literally, like in other examples such as this?

```
!!js/regexp blahblahblah
```

I think it should be treated as the following:

```
new RegExp('/efe/g/g');
```
