accidentally deleted entire iTunes Match music library - is there a way to recover?
Unfortunately, iTunes Match really isn't made to be a backup service in this way, and it can be really easy to loose stuff if you don't have other means of recovering it.

For those songs you purchased from iTunes, you should be able to still see them in the purchased list in the iTunes store, and re-add them to your library. Many other sources, like Amazon, will also allow you to re-download their files.

If you had a Time Machine backup, maybe your old library is stored there as well?

If you happen to have an iPod, and had any music synced to it, you could actually use that as a 'backup' and pull your songs from there using an application like iRip. This would only work though if you had a device with the files actually on there, as in a iPod classic or nano, or an iOS device you had downloaded music too.

Finally, you MAY be able to contact Apple Support and see if they have any way of helping, but this may take a very long time and not actually produce anything. I have had a hard time getting support on anything with Match, so replacing an entire library may even be harder. I would recommend calling them if possible.