list-tries is a Haskell library providing finite sets of list-valued keys and finite maps from list-valued keys to arbitrary values, implemented using tries and Patricia tries. It's licensed under the 3-clause BSD license.
True to its name, list-tries uses a list-based API and also stores data as lists internally in the Patricia tries. This likely results in suboptimal performance compared to e.g. using vectors at least some of the time. Furthermore, I've spent very little time on optimizing list-tries. Thus I recommend using more specialized and optimized solutions such as bytestring-trie whenever possible.
list-tries is on Hackage, the typical source for Haskell software, where you can also browse the documentation.
A local download of the source code is also available: