Alternatively, do a lot of pen-and-paper design first, including writing a few toy programs for every feature you want to add.

Mentally working your way through how a program would be interpreted and run helps a lot with working out the kinks, and in my case a least pen and paper helped me focus a lot and spot details and mistakes that would have been lost if I had been typing in some mock plaintext file.

EDIT: I'm fine with people thinking I said something stupid, so I don't mind the downvote, but I'd like to know why exactly so I can learn from the other viewpoint. What is the problem with suggesting to work out out problems on paper, including the semantic design of a programming language in particular? It's a good stress-test for "how well can I debug this in my head", for starters.