This is one of the truly venerable modules available on the CPAN, created some time around the release of 5.000 or 5.001, which is part of the reason why it has a single word name. These days, it would probably wind up with a name like Filesys::Quota, so when you look upon this module, respect its heritage.
The interface also shows its age. Like the stat function, the main quota query function returns a long list of values whose place and purpose can never be remembered; you have to look at the documentation. But that's ok too, because the documentation is well written and easy to understand. It does assume that you already have an understanding of how quotas work. Where needed, the documentation points out issues with specific operating systems.
It also handles newer architectures that allow quotas to be associated with groups (and not just users).
At some point a couple of years ago, I tried to use Quota on a Solaris 5.8 box, and the compilation failed with some sort of error to do with header files. I sent a message off to the author explaining the situation. He replied a couple of days later suggesting something to try (adding an #ifdef in a header file of the package, if memory serves). As it happened, I had fallen back to screen-scraping the output of repquota(1), so I wasn't particularly fussed. And in any event, when I had another shot at installing it some months down the track, it installed on 5.8 without a hitch.
All in all, a very useful module in its own right, while having a remarkable historical interest at the same time. Ask yourself, will you still be supporting your modules in 2017?