> Seriously speaking, your doubts are correct, my proposed
> syntax will cause a grammar conflict in the future. But I don't have good
> suggestions right now. The only thought I have:
>
> execute procedure (<value1> as a, <value2> as b, ... )
>
> But this looks quite ugly, IMHO.

As someone has already mentioned VB, why not make it
execute procedure (<value1> := a, <value2> := b, ... )