I’m still worried about making subroutines syntactic. The intent was pure mechanism at the level of EVM assembly - retaining current control flow operations and adding a Forth-style return stack. At first I only had JUMPSUBs to any JUMPDST. It was trying to write some example code that way inspired BEGINSUB - it seemed the minimum necessary structure.
For an interpreter this doesn’t present much trouble, but I can see how it would cause problems for LLVM and similar tools. So I’d ask, without time to analyze, for the minimal structure needed for the purpose.
And I suspect extended dup and swap could help.