I am trying to match a string if it is a valid "unit" in my program.

Valid units consists of:

`At least one letter, optional / or -, at least one more letter if you did the optional / or -`

Current attempt: `str.matches("[a-zA-z]*[-\\/]?[a-zA-z]*")`

Example:

```
Valid -> abc/abc
Valid -> abc
Invalid -> abc^abc
Invalid -> abc/abc

```

The invalid cases are showing as valid.