Hey there and thanks a bunch for sharing your solutions :)
I noticed that here your implementation of isSubsequenceOf, while geniously simple, fails the following test:
isSubsequenceOf "blah" "blawhoot" --> supposed to be True
I do have a solution that works, but it's so clumsy I don't want to share it ;) and I also couldn't find a good way yet to make use of as-patterns here.