I think that you may have misunderstood. I was not talking about source filter macros, but 'proper' macros.

The macro body would be an ordinary subroutine compiled by Perl in exactly the same way as any other subroutine. Then at INIT{} or CHECK() time, the calls to that subroutine would be inlined at the call site. That is, the opcode tree built for the macro body, would be cloned and inserted into the opcode tree in place of the call opcode, with references to it's formal arguments replaced by references to the actual arguments.

There would probably have to be some fairly strict restrictions on what the macro body could do, like

• no references to variables outside the scope of it's body.
• no recursion--either self or mutual.
• probably a lot of other things I haven't thought of.

I've also played with source filter macros, and got somethings to work--but they quickly get messy and never play nice with other source filters.