A few nights ago I tweeted that I had begun work on a new HAGGIS parser. This parser is actually a YASS transpiler that transpiles from SQA HAGGIS to my own YASS before interpreting and running the YASS code.
The parser will not only check if the code is valid, but it will also explain what is wrong with it. It will also be able to run it.
Whilst this is still experimental or incomplete, I have uploaded ZPE 1.7.2 with the new HAGGIS parser on to my server.
I hope people find this useful!