Avoiding sigils is a good future proofing strategy. When you find out you need a new syntax it's nice to have a set of symbols that are guaranteed not to break existing code
The way you worded this reminded me about some language extensions for the Commodore 64 and 128 that hooked into the BASIC language tokenizer. I remember one published in RUN magazine, I think for additional graphics functions, that added new BASIC instructions that were all prefixed with @. Not only did this prefix invoke the new code while interpreting, it also namespaced the addition avoiding conflicts with existing BASIC code.