However, I am not totally sure that the use of exclamation mark and question mark to start expressions makes it any more readable than embedding code inside comments.
Also not sure what a "single source for template values" means , since in ytt you can have multiple input sources
YTT fulfills its mission, but I wanted to explore a more generic approach and have the loading of libs and values using the same mechanism. Also, allowing the reusable parts to be written in YAML and not only in the additional programming language.
I aim at bringing some ideas in this area and if they make sense, I am happy to see them live, be it in Yglu, YTT or any other tool.
Also, the fact that building Yglu was fast because of YAML parser and YAQL were already existing made me explore on my own, rather than developing these ideas in modifying or coding YTT libs, what I first imagined.
About the readability, I also don't see an argument here. !? vs. #@ does not matter a lot. It only matters that !? is already understood by the YAML parser as a tag, avoiding me to write a parser (I would not have started this work). The cool thing is that tags can also be used in mapping keys.
I will rephrase the "single source for template values" into something that gives better credit, because I really meant that import mechanisms should be the same for values and other stuff (libs, functions, ...). And aslo not only as overlay.
Thanks for the inspiration and let's continue to try and relieve the YAML pain around us.